pf: Add pfsync protocol for FreeBSD 15

A new version of pfsync packet is introduced: 1500. This version solves
the issues with data alignment introduced in version 1400 and adds syncing
of information needed to sync states created by rules with af-to (original
interface, af and proto separate for wire and stack keys), of rt_af
needed for prefer-ipv6-nexthop, and of tag names.

Reviewed by: kp
Sponsored by: InnoGames GmbH
Differential Revision: https://reviews.freebsd.org/D52176