Enhance matching module with reference identity and caching improvements

- Introduced a new `RefIdentity` type to store reference details (name and className) in the matching process.
- Updated `VCache` and `SCache` structures to include references, improving the handling of reference comparisons during matching.
- Modified `cacheVirtual` and `cacheStudio` functions to support reference caching, enhancing performance and accuracy in matching.
- Improved `countOwnDiffs` function to account for reference mismatches, ensuring more precise cost calculations.
- Added comprehensive tests to validate the new reference handling and caching mechanisms.

These changes significantly enhance the efficiency and accuracy of the matching process in the application.

rojo-test/serve-tests/non_default_project/named.project.json5

@@ -0,0 +1,10 @@
+{
+  "name": "non_default_project",
+  "tree": {
+    "$className": "DataModel",
+    "ReplicatedStorage": {
+      "$className": "ReplicatedStorage",
+      "$path": "src"
+    }
+  }
+}

rojo-test/serve-tests/non_default_project/src/hello.luau

@@ -0,0 +1 @@
+return {}

rojo-test/serve-tests/non_default_project/trap/bad.rbxm

@@ -0,0 +1,2 @@
+This is not a valid rbxm file. If the snapshot system walks into this
+directory, it will error with "Malformed rbxm file: Invalid file header".