This commit adds most of the work of #21859. It introduces hs_circuit.c
functions that can handle the setup of e2e circuits for prop224 hidden
services, and also for legacy hidden service clients. Entry points are:

		prop224 circuits: hs_circuit_setup_e2e_rend_circ()
		legacy client-side circuits: hs_circuit_setup_e2e_rend_circ_legacy_client()

This commit swaps the old rendclient code to use the new API.

I didn't try to accomodate the legacy service-side code in this API, since
that's too tangled up and it would mess up the new API considerably IMO (all
this service_pending_final_cpath_ref stuff is complicated and I didn't want to
change it).

Signed-off-by: David Goulet <dgoulet@torproject.org>