MINOR: quic: Persistent congestion detection outside of controllers

MINOR: quic: Persistent congestion detection outside of controllers

We establish the persistent congestion out of any congestion controller
to improve the algorithms genericity. This path characteristic detection may
be implemented regarless of the underlying congestion control algorithm.

Send congestion (loss) event using directly quic_cc_event(), so without
qc_cc_loss_event() wrapper function around quic_cc_event().

Take the opportunity of this patch to shorten "newest_time_sent" member field
of quic_cc_event to "time_sent".