feat(tvix/store/proto): use Bytes instead of Vec<u8>

Makes use of https://github.com/tokio-rs/prost/pull/341, which makes our
bytes field cheaper to clone.

It's a bit annoying to configure due to
https://github.com/hyperium/tonic/issues/908, but the workaround does
get the job done.

Change-Id: I25714600b041bb5432d3adf5859b151e72b12778
Reviewed-on: https://cl.tvl.fyi/c/depot/+/8975
Reviewed-by: raitobezarius <tvl@lahfa.xyz>
Tested-by: BuildkiteCI
Reviewed-by: tazjin <tazjin@tvl.su>
Autosubmit: flokli <flokli@flokli.de>

tvix/store/src/nar/renderer.rs

@@ -115,7 +115,7 @@ fn walk_node(
                 None => {
                     return Err(RenderError::DirectoryNotFound(
                         digest,
-                        proto_directory_node.name.to_owned(),
+                        proto_directory_node.name.clone(),
                     ))
                 }
                 Some(proto_directory) => {