Remove the callbacks from the filesystem_store

This is should have no functional difference, these callbacks
were only used for testing and used up needless memory for live
systems. This PR should save about 32 bytes per FileEntry.

cas/store/BUILD

@@ -416,6 +416,8 @@ rust_test(
         "//util:buf_channel",
         "//util:common",
         "//util:error",
+        "//util:evicting_map",
+        "@crate_index//:async-lock",
         "@crate_index//:filetime",
         "@crate_index//:futures",
         "@crate_index//:lazy_static",
@@ -424,4 +426,5 @@ rust_test(
         "@crate_index//:tokio",
         "@crate_index//:tokio-stream",
     ],
+    proc_macro_deps = ["@crate_index//:async-trait"],
 )

cas/store/default_store_factory.rs

@@ -56,7 +56,7 @@ pub fn store_factory<'a>(
                 store_factory(&config.fast, store_manager).await?,
                 store_factory(&config.slow, store_manager).await?,
             )),
-            StoreConfig::filesystem(config) => Arc::new(FilesystemStore::new(&config).await?),
+            StoreConfig::filesystem(config) => Arc::new(<FilesystemStore>::new(&config).await?),
             StoreConfig::ref_store(config) => Arc::new(RefStore::new(&config, store_manager.clone())),
             StoreConfig::size_partitioning(config) => Arc::new(SizePartitioningStore::new(
                 &config,