Merge vendor sendmail 8.18.1 into HEAD
(cherry picked from commit d39bd2c138)
Add new source file for sendmail 8.18.1
(cherry picked from commit 19d4fb85bf)
New sendmail 8.18.1 cf file
(cherry picked from commit 1b6a5580c1)
Minor change to update these files so new freebsd*.cf files are
generated
(cherry picked from commit 2c191ba6b0)
Belatedly update version and date for sendmail 8.18.1 upgrade
(cherry picked from commit 31fbc98c94)
Add a note about sendmail 8.18.1's stricter SMTP protocol enforcement
(akin to commit 21c1f1deb6 in main)
Update import date for stable/14
Relnotes: Yes
Security: CVE-2023-51765
