MEDIUM: mux-quic: implement STOP_SENDING emission

MEDIUM: mux-quic: implement STOP_SENDING emission

Implement STOP_SENDING. This is divided in two main functions :
* qcc_abort_stream_read() which can be used by application protocol to
  request for a STOP_SENDING. This set the flag QC_SF_READ_ABORTED.
* qcs_send_reset() is a static function called after the preceding one.
  It will send a STOP_SENDING via qcc_send().

QC_SF_READ_ABORTED flag is now properly used : if activated on a stream
during qcc_recv(), <qcc.app_ops.decode_qcs> callback is skipped. Also,
abort reading on unknown unidirection remote stream is now fully
supported with the emission of a STOP_SENDING as specified by RFC 9000.

This commit is part of implementing H3 errors at the stream level. This
will allows the H3 layer to request the peer to close its endpoint for
an error on a stream.

This should be backported up to 2.7.