MDL-40047 events: Add events related to feedback responses

Adding following events related to feedback responses:-
/mod_feedback/event/response_deleted
/mod_feedback/event/response_submitted
MDL-40047 events: Add unit tests for feedback events
MDL-40047 events: Replace add_to_logs with new events in feedback
MDL-40048 events: New abstract event for old 'view all' log