Implementation of the 1.2 protocol with support for streaming. Provides
the client and server interfaces for implementing services with
streaming.
Unary behavior is mostly unchanged and avoids extra stream tracking just
for unary calls. Streaming calls are tracked to route data to the
appropriate stream as it is received.
Stricter stream ID handling, disallowing unexpected re-use of stream
IDs.
Signed-off-by: Derek McGowan <derek@mcg.dev>
