Remove metadata context from the channel stack

BUILD

build.yaml

gRPC.podspec

src/core/channel/client_channel.c

src/core/channel/client_uchannel.c

src/core/channel/client_uchannel.h

src/core/channel/compress_filter.c

src/core/channel/http_client_filter.c

src/core/channel/http_server_filter.c

src/core/channel/subchannel_call_holder.c

src/core/channel/subchannel_call_holder.h

src/core/client_config/subchannel.c

src/core/client_config/subchannel.h

src/core/compression/algorithm.c

src/core/compression/algorithm_metadata.h

src/core/surface/call.c

src/core/surface/channel.c

src/core/surface/channel.h

src/core/surface/lame_client.c

src/core/surface/server.c