Rename order in CreditRequirement (2/3)

This stage does the following:

- Includes a data migration to copy the values from old to new field.
- Changes business logic to switch to using new field.
- Deletes all code references of the old field.

common/djangoapps/util/tests/test_db.py

@@ -222,6 +222,7 @@ class MigrationTests(TestCase):
     Tests for migrations.
     """
 
+    @unittest.skip("Need to skip as part of a 3-release rollout to rename a field in the credit app. This will be unskipped in DE-1823.")
     @override_settings(MIGRATION_MODULES={})
     def test_migrations_are_in_sync(self):
         """