Core/Scripts: Add new SpellScript hook OnEffectSuccessfulDispel

Adds SpellScript hook to execute scripts after succesful dispels, example could be warlock pets Devour Magic, which should only trigger when succesfully dispelling an aura.

(cherry picked from commit ebf95e7ed7f518c54d9c4044e050d50e0dcb0c57)

Conflicts:
	src/server/game/Spells/SpellEffects.cpp