pf: Make nat-to and rdr-to work properly both on in and out rules

New-style address translation is done by nat-to and rdr-to actions on
normal match and pass rules. Those rules, when used without address
translation, can be specified without direction. But that allows users
to specify pre-routing nat and post-routing rdr. This case is not
handled properly and causes pre-routing nat to modify destination
address, as if it was a rdr rule, and post-routing rdr to modify source
address, as if it was a nat rule.

Ensure that nat-to action modifies source address and rdr-to destination
address no matter in which direction the rule is applied. The man page
for pf.conf already specifies that nat-to and rdr-to rules should be
limited to respective directions.

PR: 288577
Reviewed by: kp
MFC after: 3 days
Sponsored by: InnoGames GmbH
Differential Revision: https://reviews.freebsd.org/D53216

(cherry picked from commit 646798b6783184fb194a2d97667e05895e00c358)