Auto merge of #15080 - dati91:idlharness, r=jdm

Add Bluetooth idlharness test

<!-- Please describe your changes on the following line: -->
Add idlharness wpt test file for WebBluetooth.

---
<!-- Thank you for contributing to Servo! Please replace each `[ ]` by `[X]` when the step is complete, and replace `__` with appropriate data: -->
- [X] `./mach build -d` does not report any errors
- [X] `./mach test-tidy` does not report any errors
- [ ] These changes fix #__ (github issue number if applicable).

<!-- Either: -->
- [X] There are tests for these changes OR
- [ ] These changes do not require tests because _____

<!-- Pull requests that do not address these steps are welcome, but they will require additional verification as part of the review process. -->

<!-- Reviewable:start -->
---
This change is [<img src="https://reviewable.io/review_button.svg" height="34" align="absmiddle" alt="Reviewable"/>](https://reviewable.io/reviews/servo/servo/15080)
<!-- Reviewable:end -->

tests/wpt/mozilla/meta/MANIFEST.json

@@ -7514,6 +7514,12 @@
             "url": "/_mozilla/mozilla/bluetooth/idl-BluetoothUUID.html"
           }
         ],
+        "mozilla/bluetooth/interfaces.html": [
+          {
+            "path": "mozilla/bluetooth/interfaces.html",
+            "url": "/_mozilla/mozilla/bluetooth/interfaces.html"
+          }
+        ],
         "mozilla/bluetooth/readValue/characteristic/blocklisted-characteristic.html": [
           {
             "path": "mozilla/bluetooth/readValue/characteristic/blocklisted-characteristic.html",