MINOR: quic: use the listener for Retry and Version Negotiation emission

MINOR: quic: use the listener for Retry and Version Negotiation emission

send_retry() and send_version_negotiation() take the listener socket FD
as first argument, while send_stateless_reset() takes the listener
instance. Make the first two also take the listener instance. Also
rename their <addr> argument to <dst> to remove any ambiguity, as it is
the destination of the emitted datagram, and fix send_stateless_reset()
comment which still mentioned a FD.

This patch does not introduce any functional change. It is a
prerequisite for the following fixes on Retry, Stateless Reset and
Version Negotiation emission. As such, it should be backported with
them up to 2.8. Prior to 2.9, these functions are static functions
defined in quic_conn.c.