Core/Scripts: Adding script hooks to allow for third party scripts to modify damage dealt.

Originally from the VAS Autobalance script, slightly modified.

Only addresses Spells, Dots, and Melee Damage. I'll have look at the current modules on ways of doing this but, Environmental Damage(fire/lava/drowning), Fall Damage, and Potentially AoE aren't covered by these.

Closes #7867

Signed-off-by: Nay <dnpd.dd@gmail.com>

src/server/game/Entities/Unit/Unit.cpp

@@ -1038,6 +1038,9 @@ void Unit::CalculateSpellDamageTaken(SpellNonMeleeDamage* damageInfo, int32 dama
             break;
     }
 
+    // Script Hook For CalculateSpellDamageTaken -- Allow scripts to change the Damage post class mitigation calculations
+    sScriptMgr->ModifySpellDamageTaken(damageInfo->target, damageInfo->attacker, damage);
+
     // Calculate absorb resist
     if (damage > 0)
     {
@@ -1134,6 +1137,9 @@ void Unit::CalculateMeleeDamage(Unit* victim, uint32 damage, CalcDamageInfo* dam
     damage = MeleeDamageBonusDone(damageInfo->target, damage, damageInfo->attackType);
     damage = damageInfo->target->MeleeDamageBonusTaken(this, damage, damageInfo->attackType);
 
+    // Script Hook For CalculateMeleeDamage -- Allow scripts to change the Damage pre class mitigation calculations
+    sScriptMgr->ModifyMeleeDamage(damageInfo->target, damageInfo->attacker, damage);
+
     // Calculate armor reduction
     if (IsDamageReducedByArmor((SpellSchoolMask)(damageInfo->damageSchoolMask)))
     {