stream_op cleanup: channel, client_config changes

src/core/census/grpc_filter.c

src/core/channel/channel_stack.c

src/core/channel/channel_stack.h

src/core/channel/client_channel.c

src/core/channel/client_uchannel.c

src/core/channel/compress_filter.c

src/core/channel/connected_channel.c

src/core/channel/connected_channel.h

src/core/channel/http_client_filter.c

src/core/channel/http_server_filter.c

src/core/channel/noop_filter.c

src/core/channel/subchannel_call_holder.c

src/core/channel/subchannel_call_holder.h

src/core/client_config/lb_policies/pick_first.c

src/core/client_config/lb_policies/round_robin.c

src/core/client_config/lb_policy.c

src/core/client_config/lb_policy.h

src/core/client_config/subchannel.c

src/core/client_config/subchannel.h