Rename Call to ClientCalls.

Other classes are already following the convention that ClientFoo for
client-side, and ServerFoo for server-side. Call has been the black
sheep of the family.

- Call -> ClientCall
- Calls -> ClientCalls
- ForwardingCall* -> ForwardingClientCall*
diff --git a/compiler/src/test/golden/TestService.java.txt b/compiler/src/test/golden/TestService.java.txt
index 081ef00..e2df739 100644
--- a/compiler/src/test/golden/TestService.java.txt
+++ b/compiler/src/test/golden/TestService.java.txt
@@ -1,13 +1,13 @@
 package io.grpc.testing.integration;
 
-import static io.grpc.stub.Calls.createMethodDescriptor;
-import static io.grpc.stub.Calls.asyncUnaryCall;
-import static io.grpc.stub.Calls.asyncServerStreamingCall;
-import static io.grpc.stub.Calls.asyncClientStreamingCall;
-import static io.grpc.stub.Calls.duplexStreamingCall;
-import static io.grpc.stub.Calls.blockingUnaryCall;
-import static io.grpc.stub.Calls.blockingServerStreamingCall;
-import static io.grpc.stub.Calls.unaryFutureCall;
+import static io.grpc.stub.ClientCalls.createMethodDescriptor;
+import static io.grpc.stub.ClientCalls.asyncUnaryCall;
+import static io.grpc.stub.ClientCalls.asyncServerStreamingCall;
+import static io.grpc.stub.ClientCalls.asyncClientStreamingCall;
+import static io.grpc.stub.ClientCalls.duplexStreamingCall;
+import static io.grpc.stub.ClientCalls.blockingUnaryCall;
+import static io.grpc.stub.ClientCalls.blockingServerStreamingCall;
+import static io.grpc.stub.ClientCalls.unaryFutureCall;
 import static io.grpc.stub.ServerCalls.createMethodDefinition;
 import static io.grpc.stub.ServerCalls.asyncUnaryRequestCall;
 import static io.grpc.stub.ServerCalls.asyncStreamingRequestCall;