move critical services off, and then replace, moly

As part of legacy/trac#29817 (moved), we found out that moly.torproject.org has vastly surpassed its shelf life, having been installed in 2011. It's a big machine with multiple KVM guests, so we can't simply retire it and redistribute its guests elsewhere, at least not without filling up the rest of the infrastructure.

So we probably need to find a replacement box for moly.

Update; the replacement has arrived, it's the gnt-dal cluster, see %"trusted high performance cluster" and #40972 (closed) and so on. fallax has been partly migrated, still needs to be fixed with DRBD or rebuilt, and glue records need to be updated.

moly retirement checklist:

1. announcement
2. nagios
3. retire the host in fabric
4. remove from LDAP with ldapvi
5. power-grep
6. remove from tor-passwords
7. remove from DNSwl
8. remove from docs
9. remove from racks (wipe partially completed at 57.20%)
10. remove from reverse DNS

fallax remaining TODOs:

• convert to DRBD or rebuild (let's just rebuild)
• glue record update
• retirement of the old instance (or all of fallax if rebuilt) moved to #41107 (closed)