refactor(tvix/store): move deriver field into narinfo submessage

This information is present in the .narinfo files, it should have gone
there.

Change-Id: Ib43d0cf30c2795bf1fe77c46646174353ade0458
Reviewed-on: https://cl.tvl.fyi/c/depot/+/9794
Autosubmit: flokli <flokli@flokli.de>
Reviewed-by: Connor Brewster <cbrewster@hey.com>
Tested-by: BuildkiteCI

tvix/cli/src/tvix_store_io.rs

@@ -343,10 +343,10 @@ async fn import_path_with_pathinfo(
             nar_sha256: nar_sha256.to_vec().into(),
             signatures: vec![],
             reference_names: vec![],
+            deriver: None,
             // 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