Add contains_content_type_gated_content attribute to display items in the Sequence Metadata API. This attribute is used to display the content type gating paywall in frontend-app-learning.

Also, refactor existing timed exam code that checks for content_type_gated_content in a sequence to make it try with the new code
AA-613

lms/djangoapps/courseware/tests/test_views.py

@@ -269,8 +269,8 @@ class IndexQueryTestCase(ModuleStoreTestCase):
     NUM_PROBLEMS = 20
 
     @ddt.data(
-        (ModuleStoreEnum.Type.mongo, 10, 171),
-        (ModuleStoreEnum.Type.split, 4, 167),
+        (ModuleStoreEnum.Type.mongo, 10, 174),
+        (ModuleStoreEnum.Type.split, 4, 170),
     )
     @ddt.unpack
     def test_index_query_counts(self, store_type, expected_mongo_query_count, expected_mysql_query_count):