[PATCH 0 of 4] wireproto/setdiscovery: use call batching

[Peter Arrenbrecht]

This series adds support for call batching to wireproto's wirerepository.
It then uses this in setdiscovery to speed it up slightly.

For localrepo, it uses a stopgap solution since we don't yet have a
localpeer where localbatch could be added properly for a consistent
API across all peer classes.

It adds batching support to more wire commands than strictly necessary
just so we have this in our toolbox. We could, however, defer this in
wirerepository until needed since it's a client-only change. The server
just needs to support the "batch" command as such.