Core/Auras: Expanding functionality of SPELL_GROUP_STACK_RULE_EXCLUSIVE_SAME_EFFECT to be able to take care of aura effects inside their handlers

Currently handled:
- SPELL_AURA_MOD_RESISTANCE_PCT
- SPELL_AURA_MOD_STAT
- SPELL_AURA_MELEE_SLOW
- SPELL_AURA_MOD_MELEE_HASTE
- SPELL_AURA_MOD_DAMAGE_PERCENT_DONE

Necessary to allow stack rules such as BoK/BoS/Bok-Drums and others to be all in a target with all of the aura effects, yet with only the 'highest' effect active
Merge pull request #12233 from Trisjdc/aura_stacking

Core/Auras: Expanding functionality of SPELL_GROUP_STACK_RULE_EXCLUSIVE_SAME_EFFECT to be able to take care of aura effects inside their handlers