Make our onion services single-hop

We're running a number of onion services on our infrastructure. As of today, the reason to run these as onion services is never to hide their location, so we could get better performance (and lighter load on the Tor network) if we set them up as single-hop onion services.

Originally reported on tails/sysadmin#16409:

Also, have you considered running the Tails repos as single onion services ? Skipping the onion routing on the server side would make more bandwidth available. I feel like the repos were super slow from over here, but maybe it’s just my connection? https://blog.torproject.org/whats-new-tor-0298

Once single-hop is no longer an experimental feature, we should enable it for http-hidden and whisperback