upgrade eugeni to bullseye

eugeni is going to be a tricky bullseye upgrade, so it's not part of the large bullseye upgrade batches (#40690 (closed) or #40692 (closed)).

we might want to decide what to do with mailman (#40471 (closed)) and schleuder (#40564 (closed)) before we do the upgrade. mailman 2, in particular, is EOL so we will need to upgrade or replace it.

we might also want to consider the impact of the %improve mail services roadmap here. it's possible we might want to completely rebuild eugeni in different components instead of upgrading it.

checklist:

• warn about final destruction of (private) archives not migrated to mailman3 we made mailman2.torproject.org and actually copied the mbox archives
• follow eugeni upgrade procedure
• retire mailman2 vhost
• retire mailman2 DNS and cert
• remove lists.tpo cert
• remove mailman2 package, if not done already
• remove apache web server from eugeni, along with matching firewall rules
• cleanup/remove profile::lists code, take particular care with ssl::service[lists.tpo], see also #41850
• sync /var/lib/mailman to lists-01 again, possibly keeping just .mbox files (8.9GB instead of 34GB for the generated HTML and .txt files, so far only the mbox have been copied as part of the mailman upgrade in #40471 (closed) )
• trash /var/lib/mailman