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/store/src/tests/fixtures.rs

@@ -109,6 +109,7 @@ lazy_static! {
         }),
         references: vec![DUMMY_OUTPUT_HASH.clone()],
         narinfo: None,
+        deriver: None,
     };
 
     /// A PathInfo message with .narinfo populated.