Make sure \core\event\user_graded is triggered for every change in course total

There is a unittest introduced by MDL-40697 that validates that event is triggered for updated quiz grade. As part of MDL-47673 it was discovered that quiz generator had by default 'grade=0' which made it ungradeable. Overwriting the activity grade did not update course total.

Suspiciously only one event count assertion in related unittest core_event_user_graded_testcase::test_event_is_triggered needed fixing.

We need to make sure that additional event is always triggered when course total is also updated.