mail/mailman: fix some permission issues, realign template policy

• tighten up permissions on install dirs even more, patching bin/check_perms to not complain - fewer directories or files belong in mailman's hand or need group write permissions.

• revert 2.1.30's "make templates samples" because the upstream has always instead provided a templates/site dir here and warned users that default templates will be overwritten on updates or reinstallation https://wiki.list.org/DOC/4.48%20How%20can%20I%20change%20the%20HTML%20or%20.txt%20templates%20used%20by%20my%20mailing%20lists%3F changed templates will be written to different directories, the site, domain-specific or list-specific directory

• adjust pkg-plist such that a no-script install, a regular install with post-install script run, and check_perms agree on permissions, however with tighter write permissions than the default install, as a security-in-depth safety precaution. [1]

• revise files/pkg-install.in accordingly

• boil down files/pkg-message.in texts a little bit

• bump PORTREVISION

PR: 245853
Reported by: manu@ (IRC) [1]