test: Import some mochitests from firefox, p=#10897

* test: Import some mochitests from firefox, b=no-bug, c=tests, scripts, tabs

* feat: Added lint rules to ignore mochi tests, b=no-bug, c=tests

* chore: Finish importing tests, b=no-bug, c=workflows, tests, scripts, tabs

.github/workflows/sync-upstream.yml

@@ -95,6 +95,10 @@ jobs:
           echo "Checking if patches apply cleanly..."
           npm run import
 
+      - name: Import external tests
+        if: steps.git-check.outputs.files_changed == 'true'
+        run: python3 scripts/import_external_tests.py
+
       - name: Create pull request
         uses: peter-evans/create-pull-request@v7
         if: steps.git-check.outputs.files_changed == 'true'