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/eval/Cargo.toml

@@ -10,6 +10,7 @@ name = "tvix_eval"
 
 [dependencies]
 builtin-macros = { path = "./builtin-macros", package = "tvix-eval-builtin-macros" }
+bytes = "1.4.0"
 codemap = "0.1.3"
 codemap-diagnostic = "0.1.1"
 dirs = "4.0.0"