Improvements to notification of updated course content to groups

Identified by lsansone on MDLQA-17320.

The notification about updated course content works fine but there are some use cases that could be improved:

1. Test notifications with date restriction: no notification after date
2. Test notification with group restriction:
   1. notification for student WITHOUT group but no access
   2. notification for student IN OTHER group but no access
3. Test notification with group restriction AND course with separate group mode:
   1. notification for student WITHOUT group but no access
   2. notification for student IN OTHER group but no access
4. Test notification with group restriction AND course with separate group mode AND common setting in activity with separate group mode:
   1. notification for student WITHOUT group but no access
   2. notification for student IN OTHER group but no access