BUG/MEDIUM: quic: reset consecutive_losses on exit from recovery period (cubic)

BUG/MEDIUM: quic: reset consecutive_losses on exit from recovery period (cubic)

When exiting the recovery period and re-entering congestion avoidance,
the consecutive_losses counter was not reset. This meant that if a loss
event arrived immediately after the ACK that ended recovery, the counter
would still hold the value that triggered recovery, causing an immediate
re-entry into recovery (recovery -> CA -> recovery loop).

Resetting consecutive_losses to 0 on recovery exit matches the behavior
of resetting it on ACK in CA, ensuring a clean slate for the new
congestion avoidance period.

Must be backported to all versions.