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

Needed for https://github.com/TrinityCore/TrinityCore/issues/4313
Let's say I remove the strongest aura of all. This check will evaluate to true, thus early returning out of this `AuraEffect` handler, and not updating any of the stats.
Imagine a +1% aura, and a +5%.


> /!\ Assuming hook is called before auraeffect is applied
> /!\ and called AFTER auraeffect is actually removed
> /!\ (so `Unit::GetHighest...` doesn't iterate through it)

```
Order of actions:
- Apply +1% then +5%
  -> spellGroupVal = 0%, stat is 1%
  -> spellGroupVal = 1%, GetAmount() = 5%, stat is 5%
a) - Remove +1%
       -> spellGroupVal = 5%, GetAmount() = 1%, no effect
    - Remove +5%
       -> spellGroupVal = 0%, GetAmount() = 5%, remove
b) - Remove +5%
       -> spellGroupVal = 1%, GetAmount() = 5%, stat is 1%
    - Remove +1%
       -> spellGroupVal = 0%, GetAmount() = 1%, stat is 0%
```

So I'm giving this a go `IFF` hooks are called in the order i assume above (which is something I do not remember at all)