MEDIUM: mux-quic: implement MAX_STREAMS emission for bidir streams

MEDIUM: mux-quic: implement MAX_STREAMS emission for bidir streams

Implement the locally flow-control streams limit for opened
bidirectional streams. Add a counter which is used to count the total
number of closed streams. If this number is big enough, emit a
MAX_STREAMS frame to increase the limit of remotely opened bidirectional
streams.

This is the first commit to implement QUIC flow-control. A series of
patches should follow to complete this.

This is required to be able to handle more than 100 client requests.
This should help to validate the Multiplexing interop test.