Add initial grade signaling

Tells the Credential service about user grades when a cert is awarded
or a grade for a course with an awarded cert changes.

LEARNER-5051

lms/djangoapps/courseware/tests/test_views.py

@@ -1440,7 +1440,7 @@ class ProgressPageTests(ProgressPageBaseTests):
 
     @patch.dict(settings.FEATURES, {'ASSUME_ZERO_GRADE_IF_ABSENT_FOR_ALL_TESTS': False})
     @ddt.data(
-        (False, 44, 28),
+        (False, 45, 29),
         (True, 37, 24)
     )
     @ddt.unpack