Add events to `XCGS_Effect::RemoveEffect()`

[M3r1st]

The following 2 events would give access to the unit and effect states before and after X2Effect_Persistent::OnEffectRemoved() is called. Having only a single event can be insufficient as multiple effects can be removed in a single game state.

	EventManager.TriggerEvent('PrePersistentEffectRemoved', NewEffectState, kNewTargetState, NewGameState);
	EffectTemplate.OnEffectRemoved( ApplyEffectParameters, NewGameState, bCleansed, self );
	EventManager.TriggerEvent('PostPersistentEffectRemoved', NewEffectState, kNewTargetState, NewGameState);