refactor(tvix/store): use composition in tvix_store crate

Change-Id: Ie6290b296baba2b987f1a61c9bb4c78549ac11f1
Reviewed-on: https://cl.tvl.fyi/c/depot/+/11983
Reviewed-by: flokli <flokli@flokli.de>
Autosubmit: yuka <yuka@yuka.dev>
Tested-by: BuildkiteCI

tvix/store/src/composition.rs

@@ -0,0 +1,22 @@
+use lazy_static::lazy_static;
+
+pub use tvix_castore::composition::*;
+
+lazy_static! {
+    /// The provided registry of tvix_store, which has all the builtin
+    /// tvix_castore (BlobStore/DirectoryStore) and tvix_store
+    /// (PathInfoService) implementations.
+    pub static ref REG: Registry = {
+        let mut reg = Default::default();
+        add_default_services(&mut reg);
+        reg
+    };
+}
+
+/// Register the builtin services of tvix_castore and tvix_store with the given
+/// registry. This is useful for creating your own registry with the builtin
+/// types _and_ extra third party types.
+pub fn add_default_services(reg: &mut Registry) {
+    tvix_castore::composition::add_default_services(reg);
+    crate::pathinfoservice::register_pathinfo_services(reg);
+}