Reshuffle include/ directory layout

This CL reorganizes the include/ directory as follows:
1. The immediate subdirectories of include/ are now the stable API
   surface exposed to all embedders, with the exception of ext/.
2. ext/ contains the unstable API surface that is exposed only to chrome.

Test: builds on all configurations and passes tests
Bug: 132678367
Change-Id: If638d4b4c150fd591cd1db851283b25ff6083ed6
diff --git a/test/end_to_end_shared_memory_fuzzer.cc b/test/end_to_end_shared_memory_fuzzer.cc
index 5006afb..bb6d90e 100644
--- a/test/end_to_end_shared_memory_fuzzer.cc
+++ b/test/end_to_end_shared_memory_fuzzer.cc
@@ -20,14 +20,14 @@
 
 #include "perfetto/base/logging.h"
 #include "perfetto/base/task_runner.h"
-#include "perfetto/base/utils.h"
+#include "perfetto/ext/base/utils.h"
+#include "perfetto/ext/tracing/core/data_source_config.h"
+#include "perfetto/ext/tracing/core/data_source_descriptor.h"
+#include "perfetto/ext/tracing/core/producer.h"
+#include "perfetto/ext/tracing/core/trace_writer.h"
+#include "perfetto/ext/tracing/ipc/producer_ipc_client.h"
+#include "perfetto/ext/tracing/ipc/service_ipc_host.h"
 #include "perfetto/trace/test_event.pbzero.h"
-#include "perfetto/tracing/core/data_source_config.h"
-#include "perfetto/tracing/core/data_source_descriptor.h"
-#include "perfetto/tracing/core/producer.h"
-#include "perfetto/tracing/core/trace_writer.h"
-#include "perfetto/tracing/ipc/producer_ipc_client.h"
-#include "perfetto/tracing/ipc/service_ipc_host.h"
 #include "src/base/test/test_task_runner.h"
 #include "src/tracing/ipc/default_socket.h"
 #include "test/task_runner_thread.h"