tor-hsclient: Finish(?) plumbing up first cut of HS client connection

Ian Jacksonrequested to merge
Diziet/arti:hs into main

I believe this code "ought" to be able to connect to a hidden service.

Currently, in my tests, it panics somewhere in crates/tor-proto/src/crypto/cell.rs.

On top of !1238 (merged)

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