tcp: release nic ktls send tags when entering time wait

When under heavy load or churn, inline ktls offload NICs may run out
of hardware resources described by ktls send tags. Rather than
waiting for connections to pass through the time_wait state, reclaim
the ktls send tags early, at entry to time_wait. By preventing
potentially tens or hundreds of thousands of sessions from holding
send tags in time_wait, this allows more ktls sessions to be offloaded
to hardware.

Reviewed by: glebius, kib, nickbanks_netflix.com, rrs, tuexen
Sponsored by: Netflix
Differential Revision: https://reviews.freebsd.org/D56610