Privacy: Do not list supported encodings in hsdesc reqs.
Since not everybody has xz and/or zstd, we don't want to admit whether we support them when we are uploading or downloading an onion service descriptor. Similarly, if we aren't advertising support for an encoding, we shouldn't accept it.
Finally, while we're doing this, it made sense to have the ability to mark requests based on how anonymized they are, and reject (some) attempts to send those requests over a one-hop circuit.
Closes #1062 (closed).
Additionally, this branch resolves or downgrades the TODO HSS items in tor-dirclient, which is what I was doing when I found that issue.