Add syncback_encoded_names fixture and related tests for encoded name handling

- Introduced a new fixture `syncback_encoded_names` with various scripts and models demonstrating encoded characters in names, including `What%QUESTION%Module` and `Key%COLON%Script`.
- Added tests to validate the correct handling of encoded names during directory conversions, ensuring that the filesystem names match the expected encoded formats.
- Updated `change_processor.rs` and `api.rs` to improve file handling and metadata management related to encoded names, enhancing overall robustness and consistency in operations.

rojo-test/serve-tests/syncback_encoded_names/default.project.json5

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