MDL-45641 event: Option to trigger user event manually

On some pages full user data is not stored before user_created/
user_updated event is triggred. So giving option to trigger that
manually, so it can be triggred after all data is saved
MDL-45641 event: unit test for optional user_created/updated event trigger
MDL-45641 event: Removed multiple user_updated event trigger

user_updated event was being triggred while
setting password, which is not correct. It now
trigger user_password_updated event. Few more
modifications done:
1. Correct event is being triggred.
2. Event is only triggred when password is chnaged.
3. Password is updated via single api.
4. Updated unit test