Merge remote-tracking branch 'upstream/master' into fixit_call_c

src/core/surface/call.c

src/core/transport/chttp2/frame_data.h

src/core/transport/chttp2/hpack_encoder.c

src/core/transport/chttp2/incoming_metadata.c

src/core/transport/chttp2/incoming_metadata.h

src/csharp/Grpc.Core/Channel.cs

src/csharp/Grpc.Core/Internal/ClientResponseStream.cs

...arp/Grpc.Core/Internal/NativeMetadataCredentialsPlugin.cs

src/csharp/Grpc.Core/Internal/ServerCallHandler.cs

src/csharp/Grpc.Core/Internal/ServerRequestStream.cs

src/csharp/Grpc.Core/Server.cs

src/csharp/Grpc.Core/Utils/AsyncStreamExtensions.cs

test/core/security/credentials_test.c

test/core/surface/byte_buffer_reader_test.c