BUG/MINOR: mux-quic: always report error to SC on RESET_STREAM emission

BUG/MINOR: mux-quic: always report error to SC on RESET_STREAM emission

On RESET_STREAM emission, the stream Tx channel is closed. This event
must be reported to stream-conn layer to interrupt future send
operations.

Previously, se_fl_set_error() was manually invocated before/after
qcc_reset_stream(). Change this by moving se_fl_set_error() invocation
into the latter. This ensures that notification won't be forget, most
notably in HTTP/3 layer.

In most cases, behavior should be identical as both functions were
called together unless not necessary. However, there is one exception
which could cause a RESET_STREAM emission without error notification :
this happens on H3 trailers parsing error. All other H3 errors happen
before the stream-layer creation and thus the error is notified on
stream creation. This regression has been caused by the following patch :

  152beeec34baed98ad4c186454ddb25e4c496b50
  MINOR: mux-quic: report error on stream-endpoint earlier

Thus it should be backported up to 2.7.

Note that the case described above did not cause any crash or protocol
error. This is because currently MUX QUIC snd_buf operation silently
reset buffer on transmission if QCS is already closed locally. This will
however be removed in a future commit so the current patch is necessary
to prevent an invalid behavior.

(cherry picked from commit 0a69750a98bbf4c8d9ab2c84e3890956116dbfa0)
Signed-off-by: Christopher Faulet <cfaulet@haproxy.com>