mirror TPA ex-gitolite repositories to GitLab

in #41219 (closed), we migrated and archived a lot of repositories to gitlab, and that worked well to pave the way to the remaining migration in #41215 (closed). but now we lost IRC and email notifications on some of the remaining active repos.

i'm considering bringing back IRC notifications by mirroring the repositories here. the authoritative copies of the repositories would stay on the trusted servers, but we would keep mirrors here, pushed with project-specific deploy keys. it seems like all those repositories are actually publicly visible in gitweb, and have been since at least 2018 according to the wayback machine, so no need to keep those private.

we would not deploy email notifications, as that is something we don't have on gitlab yet (gitlab#71).

those repositories are:

• dns/auto-dns (migrated to nevii)
• dns/dns-helpers (migrated to nevii)
• dns/domains (migrated to nevii)
• dns/mini-nag (migrated to nevii)
• letsencrypt-domains (migrated to nevii)
• tor-nagios (migrated to nagios)
• tor-passwords (migrated to pauli) we do not copy this confidential data to gitlab, and just disable email notifications (which we didn't have in the first place for that repo)
• tor-puppet (see #29387 instead)

@lavamind thoughts?