net/foreman-proxy: Update 3.13.0 => 3.18.1

Changelog:
https://github.com/theforeman/smart-proxy/blob/3.18.1/CHANGELOG

Commit log:
https://github.com/theforeman/smart-proxy/compare/3.13.0...3.18.1

Improve port:

• Fix warnings from portclippy.
• Fix build with USERS/GROUPS not in UIDs/GIDs.
• In do-install:
  • Merge MKDIRs.
  • Replace "LN -s" with "RLN".
  • Replace "CP -r" in for loop with single COPYTREE_SHARE.
  • Merge INSTALL_SCRIPTs.
  • Replace "${PREFIX}/etc/foreman-proxy" with "${ETCDIR}".
• Replace "${PREFIX}/etc/foreman-proxy" with "${ETCDIR}" in rc script.

PR: 294845
Sponsored by: UNIS Labs
Co-authored-by: Vladimir Druzenko <vvd@FreeBSD.org>