MINOR: quic: convert qc_stream_desc release field to flags

MINOR: quic: convert qc_stream_desc release field to flags

qc_stream_desc had a field <release> used as a boolean. Convert it with
a new <flags> field and QC_SD_FL_RELEASE value as equivalent.

The purpose of this patch is to be able to extend qc_stream_desc by
adding newer flags values. This patch is required for the following
patch
  BUG/MEDIUM: quic: handle retransmit for standalone FIN STREAM

As such, it must be backported prior to it.

(cherry picked from commit bb9ac256a1e5468535b8242dc762e7bb0d9a8bf3)
Signed-off-by: Christopher Faulet <cfaulet@haproxy.com>