reqwest has no UDS transport, so unix: upstreams dial the socket
directly with a raw hyper/1.1 client per request instead. http(s)://
upstreams are unaffected (still go through the existing reqwest path).
Adds hyper (client, http1), hyper-util (tokio IO adapter), and
http-body-util as direct hive-ag3nt dependencies - all three were
already present transitively via reqwest, this just uses them
directly for the new code path.
