mail/opensmtpd-table-sqlite: new port

This port replaces mail/opensmtpd-extras-table-sqlite.

The opensmtpd-extras-table-* ports got broken by the latest update of
OpenSMTPD, see my message on the mailing list:
https://lists.freebsd.org/archives/dev-commits-ports-main/2025-January/134537.html

I have requested action by fluffy@ both on the message linked above and
privately via email, but I haven't got any response back.

At this point, I want to unblock my workflow and be able to upgrade
OpenSMTPD. I don't have plans to provide alternatives to all the
opensmtpd-extras-table-* ports.