migration of gettor into rdsys

We have reimplemented gettor as part of rdsys. The plan is to put that into production by the end of the month.

The tasks I know of that are needed for this migration:

• create new rdsys-frontend-01 VM with rdsys and gettor users with sudo for all anti-censorship team.
• expose the rdsys-backend (localhost:7100/resources-stream) in apache from polyanthum to be reachable from rdsys-frontend-01 (and only from that host)
• on rdsys-frontend-01, setup a dovecot imap-only mailbox (like gitlab and civicrm) where gettor@torproject.org emails arrive. (gettor@torproject.org emails are currently arriving to gettor-01 and is being sent to gettor over a postfix pipe script), that implies:
• have a smtp server to send email with gettor@torproject.org email address. Doesn't need to be in the same machine, rdsys has support to do plain auth. should just be localhost delivery, make rdsys-frontend-01 a "mailhost" in puppet
• have a metrics endpoint for prometheus metrics. https://rdsys-frontend.torproject.org/metrics rdsys-gettor.torproject.org/metrics pointed to localhost:7700/metrics
• change the gettor@torproject.org forward on eugeni to point to gettor@rdsys-frontend.torproject.org
• remove gettor-01 machine as is not used anymore, needs coordination with anti-censorship team see #40915 (closed)

The actual move of the gettor@torproject.org email address into it's own imap server and the shutting down of gettor-01 need coordination with the anti-censorship team. And can't happen before June 27th, as we'll not be ready on rdsys side.