[9.18] Drop FreeBSD 12

Support for FreeBSD 12.4, the last FreeBSD 12.x release, ended on December 31, 2023.

Link: https://www.freebsd.org/security/unsupported/

Move the --with-readline=editline ./configure option to FreeBSD 14.

(cherry picked from commit 98bfa223)

Backport of !8670 (merged).