feat(tvix/nix-compat): add narinfo parsing and serialisation

Change-Id: I72c63414794642ca8d85c3f635f49db888420c40
Reviewed-on: https://cl.tvl.fyi/c/depot/+/9852
Reviewed-by: flokli <flokli@flokli.de>
Tested-by: BuildkiteCI

tvix/nix-compat/src/lib.rs

@@ -1,6 +1,7 @@
 pub(crate) mod aterm;
 pub mod derivation;
 pub mod nar;
+pub mod narinfo;
 pub mod nixbase32;
 pub mod nixhash;
 pub mod store_path;