Merge branch 'master' into uv_core_transport

BUILD

CMakeLists.txt

Makefile

build.yaml

doc/interop-test-descriptions.md

include/grpc++/security/credentials.h

src/core/ext/client_channel/client_channel.c

src/core/ext/client_channel/method_config.c

src/core/ext/client_channel/method_config.h

src/core/ext/transport/chttp2/transport/chttp2_transport.c

src/core/lib/channel/message_size_filter.c

src/core/lib/iomgr/udp_server.c

src/core/lib/iomgr/udp_server.h

src/core/lib/transport/mdstr_hash_table.c

src/core/lib/transport/mdstr_hash_table.h

src/cpp/client/cronet_credentials.cc

src/csharp/Grpc.Auth/GoogleAuthInterceptors.cs

src/csharp/Grpc.Core/DefaultCallInvoker.cs

src/csharp/Grpc.Core/Grpc.Core.csproj

src/csharp/Grpc.Core/GrpcEnvironment.cs