Merge github.com:grpc/grpc into tell-the-world-about-ALL-the-things

doc/interop-test-descriptions.md

include/grpc++/channel_interface.h

include/grpc++/stream.h

src/core/channel/client_channel.c

src/cpp/client/channel.cc

src/cpp/client/channel.h

src/objective-c/GRPCClient/GRPCCall+Tests.h

src/objective-c/GRPCClient/GRPCCall+Tests.m

src/objective-c/GRPCClient/private/GRPCHost.m

src/objective-c/tests/GRPCClientTests.m

src/objective-c/tests/InteropTests.h

src/objective-c/tests/InteropTests.m

templates/tools/run_tests/tests.json.template

...end2end/fixtures/chttp2_simple_ssl_fullstack_with_proxy.c

...ore/end2end/fixtures/chttp2_socket_pair_with_grpc_trace.c

test/core/end2end/gen_build_json.py

...2end/tests/request_response_with_payload_and_call_creds.c

test/cpp/end2end/end2end_test.cc

tools/buildgen/plugins/expand_bin_attrs.py

tools/run_tests/run_tests.py