Start to implement OnionService::new (part 1)
This is the first part of wiring up the pieces of our onion service implementation.
It doesn't work—there are a few interface mismatches and questions I have here.
@gabi-250 @Diziet could you look over the new TODO HSS questions in this branch and see if you have answers for any of them? In particular, I'm wondering about the cases where Publisher and IptManager handle things differently, and hoping that you can decide when I should write an adapter between them, and when they should converge in order to take the same kind of information.