refactor(tvix/store/pathinfosvc): use Arc<dyn …>

This removes the use of generics, like previously done with Blob and
Directory services.

Change-Id: I7cc8bd1439b026c88e80c11e38aafc63c74e5e84
Reviewed-on: https://cl.tvl.fyi/c/depot/+/8751
Tested-by: BuildkiteCI
Autosubmit: flokli <flokli@flokli.de>
Reviewed-by: tazjin <tazjin@tvl.su>

tvix/store/src/pathinfoservice/mod.rs

@@ -10,7 +10,7 @@ pub use self::sled::SledPathInfoService;
 
 /// The base trait all PathInfo services need to implement.
 /// This is a simple get and put of [proto::Directory], returning their digest.
-pub trait PathInfoService {
+pub trait PathInfoService: Send + Sync {
     /// Retrieve a PathInfo message by the output digest.
     fn get(&self, digest: [u8; 20]) -> Result<Option<proto::PathInfo>, Error>;