Fixing additional tests

Fixing some of the existing failing tests in the CI process.

Specifically:

- gcp_appengine_firewall_rule: modified validation to support the
  default firewall rule
- gcp_cloudfunctions_cloud_function: bootstrapping the required GS
  bucket and files for creating a valid cloud function.
  - Slight update to the functionality, which now requires a runtime
    specified for new functions.
-

test-fixtures/cloud-function-source/main.py

@@ -0,0 +1,9 @@
+import functions_framework
+
+# Register an HTTP function with the Functions Framework
+@functions_framework.http
+def helloGET(request):
+    # Your code here
+
+    # Return an HTTP response
+    return "OK"