1. Hydra currently queries for multiple path infos at once, so let us
make a connection item for that.
2. The minimum of the two versions should always be used, see #9584.
(The issue remains open because the daemon protocol needs to be
likewise updated.)
Factor out `ServeProto::BasicClientConnection` for Hydra to share
- `queryValidPaths`: Hydra uses the lock argument differently than Nix,
so we un-hard-code it.
- `buildDerivationRequest`: Just the request half, as Hydra does some
things between requesting and responding.
Co-authored-by: Robert Hensing <roberth@users.noreply.github.com>
