wireproto: port lookup to wire protocol v2
This is pretty straightforward. We don't yet handle errors because we
don't have an error handling mechanism in place yet.
I'm also tempted to fold this into `known`. We'll come back to this
later.
Differential Revision: https://phab.mercurial-scm.org/D3205
wireproto: port pushkey command to wire protocol version 2
It doesn't do output redirection yet. And I'd love to generally overhaul
the pushkey protocol for wire protocol version 2. But this will be a bit
of effort. Let's do it as a follow-up.
Differential Revision: https://phab.mercurial-scm.org/D3204