Reorganize ext tree

- filters live under filters
- lb_policy, resolver implementations (being part of client_channel) live under client_channel
diff --git a/CMakeLists.txt b/CMakeLists.txt
index 4a69b9e..2b646bb 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -1083,47 +1083,47 @@
   src/core/tsi/transport_security.c
   src/core/ext/transport/chttp2/server/chttp2_server.c
   src/core/ext/transport/chttp2/client/secure/secure_channel_create.c
-  src/core/ext/client_channel/channel_connectivity.c
-  src/core/ext/client_channel/client_channel.c
-  src/core/ext/client_channel/client_channel_factory.c
-  src/core/ext/client_channel/client_channel_plugin.c
-  src/core/ext/client_channel/connector.c
-  src/core/ext/client_channel/http_connect_handshaker.c
-  src/core/ext/client_channel/http_proxy.c
-  src/core/ext/client_channel/lb_policy.c
-  src/core/ext/client_channel/lb_policy_factory.c
-  src/core/ext/client_channel/lb_policy_registry.c
-  src/core/ext/client_channel/parse_address.c
-  src/core/ext/client_channel/proxy_mapper.c
-  src/core/ext/client_channel/proxy_mapper_registry.c
-  src/core/ext/client_channel/resolver.c
-  src/core/ext/client_channel/resolver_factory.c
-  src/core/ext/client_channel/resolver_registry.c
-  src/core/ext/client_channel/retry_throttle.c
-  src/core/ext/client_channel/subchannel.c
-  src/core/ext/client_channel/subchannel_index.c
-  src/core/ext/client_channel/uri_parser.c
+  src/core/ext/filters/client_channel/channel_connectivity.c
+  src/core/ext/filters/client_channel/client_channel.c
+  src/core/ext/filters/client_channel/client_channel_factory.c
+  src/core/ext/filters/client_channel/client_channel_plugin.c
+  src/core/ext/filters/client_channel/connector.c
+  src/core/ext/filters/client_channel/http_connect_handshaker.c
+  src/core/ext/filters/client_channel/http_proxy.c
+  src/core/ext/filters/client_channel/lb_policy.c
+  src/core/ext/filters/client_channel/lb_policy_factory.c
+  src/core/ext/filters/client_channel/lb_policy_registry.c
+  src/core/ext/filters/client_channel/parse_address.c
+  src/core/ext/filters/client_channel/proxy_mapper.c
+  src/core/ext/filters/client_channel/proxy_mapper_registry.c
+  src/core/ext/filters/client_channel/resolver.c
+  src/core/ext/filters/client_channel/resolver_factory.c
+  src/core/ext/filters/client_channel/resolver_registry.c
+  src/core/ext/filters/client_channel/retry_throttle.c
+  src/core/ext/filters/client_channel/subchannel.c
+  src/core/ext/filters/client_channel/subchannel_index.c
+  src/core/ext/filters/client_channel/uri_parser.c
   src/core/ext/transport/chttp2/client/chttp2_connector.c
   src/core/ext/transport/chttp2/server/insecure/server_chttp2.c
   src/core/ext/transport/chttp2/server/insecure/server_chttp2_posix.c
   src/core/ext/transport/chttp2/client/insecure/channel_create.c
   src/core/ext/transport/chttp2/client/insecure/channel_create_posix.c
-  src/core/ext/lb_policy/grpclb/grpclb.c
-  src/core/ext/lb_policy/grpclb/grpclb_channel_secure.c
-  src/core/ext/lb_policy/grpclb/load_balancer_api.c
-  src/core/ext/lb_policy/grpclb/proto/grpc/lb/v1/load_balancer.pb.c
+  src/core/ext/filters/client_channel/lb_policy/grpclb/grpclb.c
+  src/core/ext/filters/client_channel/lb_policy/grpclb/grpclb_channel_secure.c
+  src/core/ext/filters/client_channel/lb_policy/grpclb/load_balancer_api.c
+  src/core/ext/filters/client_channel/lb_policy/grpclb/proto/grpc/lb/v1/load_balancer.pb.c
   third_party/nanopb/pb_common.c
   third_party/nanopb/pb_decode.c
   third_party/nanopb/pb_encode.c
-  src/core/ext/lb_policy/pick_first/pick_first.c
-  src/core/ext/lb_policy/round_robin/round_robin.c
-  src/core/ext/resolver/dns/c_ares/dns_resolver_ares.c
-  src/core/ext/resolver/dns/c_ares/grpc_ares_ev_driver_posix.c
-  src/core/ext/resolver/dns/c_ares/grpc_ares_wrapper.c
-  src/core/ext/resolver/dns/native/dns_resolver.c
-  src/core/ext/resolver/sockaddr/sockaddr_resolver.c
-  src/core/ext/load_reporting/load_reporting.c
-  src/core/ext/load_reporting/load_reporting_filter.c
+  src/core/ext/filters/client_channel/lb_policy/pick_first/pick_first.c
+  src/core/ext/filters/client_channel/lb_policy/round_robin/round_robin.c
+  src/core/ext/filters/client_channel/resolver/dns/c_ares/dns_resolver_ares.c
+  src/core/ext/filters/client_channel/resolver/dns/c_ares/grpc_ares_ev_driver_posix.c
+  src/core/ext/filters/client_channel/resolver/dns/c_ares/grpc_ares_wrapper.c
+  src/core/ext/filters/client_channel/resolver/dns/native/dns_resolver.c
+  src/core/ext/filters/client_channel/resolver/sockaddr/sockaddr_resolver.c
+  src/core/ext/filters/load_reporting/load_reporting.c
+  src/core/ext/filters/load_reporting/load_reporting_filter.c
   src/core/ext/census/base_resources.c
   src/core/ext/census/context.c
   src/core/ext/census/gen/census.pb.c
@@ -1379,26 +1379,26 @@
   src/core/ext/transport/chttp2/transport/varint.c
   src/core/ext/transport/chttp2/transport/writing.c
   src/core/ext/transport/chttp2/alpn/alpn.c
-  src/core/ext/client_channel/channel_connectivity.c
-  src/core/ext/client_channel/client_channel.c
-  src/core/ext/client_channel/client_channel_factory.c
-  src/core/ext/client_channel/client_channel_plugin.c
-  src/core/ext/client_channel/connector.c
-  src/core/ext/client_channel/http_connect_handshaker.c
-  src/core/ext/client_channel/http_proxy.c
-  src/core/ext/client_channel/lb_policy.c
-  src/core/ext/client_channel/lb_policy_factory.c
-  src/core/ext/client_channel/lb_policy_registry.c
-  src/core/ext/client_channel/parse_address.c
-  src/core/ext/client_channel/proxy_mapper.c
-  src/core/ext/client_channel/proxy_mapper_registry.c
-  src/core/ext/client_channel/resolver.c
-  src/core/ext/client_channel/resolver_factory.c
-  src/core/ext/client_channel/resolver_registry.c
-  src/core/ext/client_channel/retry_throttle.c
-  src/core/ext/client_channel/subchannel.c
-  src/core/ext/client_channel/subchannel_index.c
-  src/core/ext/client_channel/uri_parser.c
+  src/core/ext/filters/client_channel/channel_connectivity.c
+  src/core/ext/filters/client_channel/client_channel.c
+  src/core/ext/filters/client_channel/client_channel_factory.c
+  src/core/ext/filters/client_channel/client_channel_plugin.c
+  src/core/ext/filters/client_channel/connector.c
+  src/core/ext/filters/client_channel/http_connect_handshaker.c
+  src/core/ext/filters/client_channel/http_proxy.c
+  src/core/ext/filters/client_channel/lb_policy.c
+  src/core/ext/filters/client_channel/lb_policy_factory.c
+  src/core/ext/filters/client_channel/lb_policy_registry.c
+  src/core/ext/filters/client_channel/parse_address.c
+  src/core/ext/filters/client_channel/proxy_mapper.c
+  src/core/ext/filters/client_channel/proxy_mapper_registry.c
+  src/core/ext/filters/client_channel/resolver.c
+  src/core/ext/filters/client_channel/resolver_factory.c
+  src/core/ext/filters/client_channel/resolver_registry.c
+  src/core/ext/filters/client_channel/retry_throttle.c
+  src/core/ext/filters/client_channel/subchannel.c
+  src/core/ext/filters/client_channel/subchannel_index.c
+  src/core/ext/filters/client_channel/uri_parser.c
   src/core/lib/http/httpcli_security_connector.c
   src/core/lib/security/context/security_context.c
   src/core/lib/security/credentials/composite/composite_credentials.c
@@ -1427,8 +1427,8 @@
   src/core/tsi/ssl_transport_security.c
   src/core/tsi/transport_security.c
   src/core/ext/transport/chttp2/client/chttp2_connector.c
-  src/core/ext/load_reporting/load_reporting.c
-  src/core/ext/load_reporting/load_reporting_filter.c
+  src/core/ext/filters/load_reporting/load_reporting.c
+  src/core/ext/filters/load_reporting/load_reporting_filter.c
   src/core/plugin_registry/grpc_cronet_plugin_registry.c
 )
 
@@ -1951,42 +1951,42 @@
   src/core/ext/transport/chttp2/client/insecure/channel_create.c
   src/core/ext/transport/chttp2/client/insecure/channel_create_posix.c
   src/core/ext/transport/chttp2/client/chttp2_connector.c
-  src/core/ext/client_channel/channel_connectivity.c
-  src/core/ext/client_channel/client_channel.c
-  src/core/ext/client_channel/client_channel_factory.c
-  src/core/ext/client_channel/client_channel_plugin.c
-  src/core/ext/client_channel/connector.c
-  src/core/ext/client_channel/http_connect_handshaker.c
-  src/core/ext/client_channel/http_proxy.c
-  src/core/ext/client_channel/lb_policy.c
-  src/core/ext/client_channel/lb_policy_factory.c
-  src/core/ext/client_channel/lb_policy_registry.c
-  src/core/ext/client_channel/parse_address.c
-  src/core/ext/client_channel/proxy_mapper.c
-  src/core/ext/client_channel/proxy_mapper_registry.c
-  src/core/ext/client_channel/resolver.c
-  src/core/ext/client_channel/resolver_factory.c
-  src/core/ext/client_channel/resolver_registry.c
-  src/core/ext/client_channel/retry_throttle.c
-  src/core/ext/client_channel/subchannel.c
-  src/core/ext/client_channel/subchannel_index.c
-  src/core/ext/client_channel/uri_parser.c
-  src/core/ext/resolver/dns/c_ares/dns_resolver_ares.c
-  src/core/ext/resolver/dns/c_ares/grpc_ares_ev_driver_posix.c
-  src/core/ext/resolver/dns/c_ares/grpc_ares_wrapper.c
-  src/core/ext/resolver/dns/native/dns_resolver.c
-  src/core/ext/resolver/sockaddr/sockaddr_resolver.c
-  src/core/ext/load_reporting/load_reporting.c
-  src/core/ext/load_reporting/load_reporting_filter.c
-  src/core/ext/lb_policy/grpclb/grpclb.c
-  src/core/ext/lb_policy/grpclb/grpclb_channel.c
-  src/core/ext/lb_policy/grpclb/load_balancer_api.c
-  src/core/ext/lb_policy/grpclb/proto/grpc/lb/v1/load_balancer.pb.c
+  src/core/ext/filters/client_channel/channel_connectivity.c
+  src/core/ext/filters/client_channel/client_channel.c
+  src/core/ext/filters/client_channel/client_channel_factory.c
+  src/core/ext/filters/client_channel/client_channel_plugin.c
+  src/core/ext/filters/client_channel/connector.c
+  src/core/ext/filters/client_channel/http_connect_handshaker.c
+  src/core/ext/filters/client_channel/http_proxy.c
+  src/core/ext/filters/client_channel/lb_policy.c
+  src/core/ext/filters/client_channel/lb_policy_factory.c
+  src/core/ext/filters/client_channel/lb_policy_registry.c
+  src/core/ext/filters/client_channel/parse_address.c
+  src/core/ext/filters/client_channel/proxy_mapper.c
+  src/core/ext/filters/client_channel/proxy_mapper_registry.c
+  src/core/ext/filters/client_channel/resolver.c
+  src/core/ext/filters/client_channel/resolver_factory.c
+  src/core/ext/filters/client_channel/resolver_registry.c
+  src/core/ext/filters/client_channel/retry_throttle.c
+  src/core/ext/filters/client_channel/subchannel.c
+  src/core/ext/filters/client_channel/subchannel_index.c
+  src/core/ext/filters/client_channel/uri_parser.c
+  src/core/ext/filters/client_channel/resolver/dns/c_ares/dns_resolver_ares.c
+  src/core/ext/filters/client_channel/resolver/dns/c_ares/grpc_ares_ev_driver_posix.c
+  src/core/ext/filters/client_channel/resolver/dns/c_ares/grpc_ares_wrapper.c
+  src/core/ext/filters/client_channel/resolver/dns/native/dns_resolver.c
+  src/core/ext/filters/client_channel/resolver/sockaddr/sockaddr_resolver.c
+  src/core/ext/filters/load_reporting/load_reporting.c
+  src/core/ext/filters/load_reporting/load_reporting_filter.c
+  src/core/ext/filters/client_channel/lb_policy/grpclb/grpclb.c
+  src/core/ext/filters/client_channel/lb_policy/grpclb/grpclb_channel.c
+  src/core/ext/filters/client_channel/lb_policy/grpclb/load_balancer_api.c
+  src/core/ext/filters/client_channel/lb_policy/grpclb/proto/grpc/lb/v1/load_balancer.pb.c
   third_party/nanopb/pb_common.c
   third_party/nanopb/pb_decode.c
   third_party/nanopb/pb_encode.c
-  src/core/ext/lb_policy/pick_first/pick_first.c
-  src/core/ext/lb_policy/round_robin/round_robin.c
+  src/core/ext/filters/client_channel/lb_policy/pick_first/pick_first.c
+  src/core/ext/filters/client_channel/lb_policy/round_robin/round_robin.c
   src/core/ext/census/base_resources.c
   src/core/ext/census/context.c
   src/core/ext/census/gen/census.pb.c
@@ -2226,6 +2226,7 @@
   src/core/lib/channel/handshaker_registry.c
   src/core/lib/channel/http_client_filter.c
   src/core/lib/channel/http_server_filter.c
+  src/core/lib/channel/max_age_filter.c
   src/core/lib/channel/message_size_filter.c
   src/core/lib/compression/compression.c
   src/core/lib/compression/message_compress.c
@@ -2698,26 +2699,26 @@
   src/core/ext/transport/chttp2/transport/varint.c
   src/core/ext/transport/chttp2/transport/writing.c
   src/core/ext/transport/chttp2/alpn/alpn.c
-  src/core/ext/client_channel/channel_connectivity.c
-  src/core/ext/client_channel/client_channel.c
-  src/core/ext/client_channel/client_channel_factory.c
-  src/core/ext/client_channel/client_channel_plugin.c
-  src/core/ext/client_channel/connector.c
-  src/core/ext/client_channel/http_connect_handshaker.c
-  src/core/ext/client_channel/http_proxy.c
-  src/core/ext/client_channel/lb_policy.c
-  src/core/ext/client_channel/lb_policy_factory.c
-  src/core/ext/client_channel/lb_policy_registry.c
-  src/core/ext/client_channel/parse_address.c
-  src/core/ext/client_channel/proxy_mapper.c
-  src/core/ext/client_channel/proxy_mapper_registry.c
-  src/core/ext/client_channel/resolver.c
-  src/core/ext/client_channel/resolver_factory.c
-  src/core/ext/client_channel/resolver_registry.c
-  src/core/ext/client_channel/retry_throttle.c
-  src/core/ext/client_channel/subchannel.c
-  src/core/ext/client_channel/subchannel_index.c
-  src/core/ext/client_channel/uri_parser.c
+  src/core/ext/filters/client_channel/channel_connectivity.c
+  src/core/ext/filters/client_channel/client_channel.c
+  src/core/ext/filters/client_channel/client_channel_factory.c
+  src/core/ext/filters/client_channel/client_channel_plugin.c
+  src/core/ext/filters/client_channel/connector.c
+  src/core/ext/filters/client_channel/http_connect_handshaker.c
+  src/core/ext/filters/client_channel/http_proxy.c
+  src/core/ext/filters/client_channel/lb_policy.c
+  src/core/ext/filters/client_channel/lb_policy_factory.c
+  src/core/ext/filters/client_channel/lb_policy_registry.c
+  src/core/ext/filters/client_channel/parse_address.c
+  src/core/ext/filters/client_channel/proxy_mapper.c
+  src/core/ext/filters/client_channel/proxy_mapper_registry.c
+  src/core/ext/filters/client_channel/resolver.c
+  src/core/ext/filters/client_channel/resolver_factory.c
+  src/core/ext/filters/client_channel/resolver_registry.c
+  src/core/ext/filters/client_channel/retry_throttle.c
+  src/core/ext/filters/client_channel/subchannel.c
+  src/core/ext/filters/client_channel/subchannel_index.c
+  src/core/ext/filters/client_channel/uri_parser.c
   src/core/ext/transport/chttp2/server/insecure/server_chttp2.c
   src/core/ext/transport/chttp2/server/insecure/server_chttp2_posix.c
   src/core/ext/transport/chttp2/server/chttp2_server.c
@@ -3255,6 +3256,7 @@
   src/core/lib/channel/handshaker_registry.c
   src/core/lib/channel/http_client_filter.c
   src/core/lib/channel/http_server_filter.c
+  src/core/lib/channel/max_age_filter.c
   src/core/lib/channel/message_size_filter.c
   src/core/lib/compression/compression.c
   src/core/lib/compression/message_compress.c