MEDIUM: quic: send CONNECTION_CLOSE on released MUX

MEDIUM: quic: send CONNECTION_CLOSE on released MUX

Send a CONNECTION_CLOSE if the MUX has been released and all STREAM data
are acknowledged. This is useful to prevent a client from trying to use
a connection which have the upper layer closed.

To implement this a new function qc_check_close_on_released_mux() has
been added. It is called on QUIC MUX release notification and each time
a qc_stream_desc has been released.

This commit is associated with the previous one :
  MINOR: mux-quic/h3: schedule CONNECTION_CLOSE on app release
Both patches are required to prevent the risk of browsers stuck on
webpage loading if MUX has been released. On CONNECTION_CLOSE reception,
the client will reopen a new QUIC connection.