feat(tvix/store): implement PathInfoService with sled

This uses [sled](https://github.com/spacejam/sled) to store PathInfo
objects.

Change-Id: I12e8032e5562af8f884efa23a78049fd1108fdbc
Reviewed-on: https://cl.tvl.fyi/c/depot/+/7726
Reviewed-by: tazjin <tazjin@tvl.su>
Tested-by: BuildkiteCI

tvix/store/src/lib.rs

@@ -4,7 +4,7 @@ pub mod store_path;
 
 pub mod dummy_blob_service;
 pub mod dummy_directory_service;
-pub mod dummy_path_info_service;
+pub mod sled_path_info_service;
 
 #[cfg(test)]
 mod tests;