feat(tvix/store/protos): add Deriver field to PathInfo

This uses the newly introduced StorePath message type to add a Deriver
field to the PathInfo message.

Support for validation is added to both the golang and rust
implementation. This includes extending unit tests.

Change-Id: Ifc3eb3263fa25b9eec260db354cd74234c40af7e
Reviewed-on: https://cl.tvl.fyi/c/depot/+/9647
Reviewed-by: Connor Brewster <cbrewster@hey.com>
Tested-by: BuildkiteCI

tvix/cli/src/tvix_store_io.rs

@@ -346,6 +346,7 @@ async fn import_path_with_pathinfo(
             // TODO: narinfo for talosctl.src contains `CA: fixed:r:sha256:1x13j5hy75221bf6kz7cpgld9vgic6bqx07w5xjs4pxnksj6lxb6`
             // do we need this anywhere?
         }),
+        deriver: None,
     };
 
     // put into [PathInfoService], and return the [PathInfo] that we get