Core/Auras: Reimplement SPELL_AURA_MOD_ARMOR_PENETRATION_PCT, it is back from the dead

Port From (https://github.com/TrinityCore/TrinityCore/commit/11f6576f04688fb89d97e2bbe7ae97a8b6585415)

Source/Framework/Constants/Spells/SpellAuraConst.cs

@@ -287,8 +287,8 @@ namespace Framework.Constants
         Unk277 = 277,  // Old ModMaxAffectedTargets. Unused 4.3.4
         ModDisarmRanged = 278,
         InitializeImages = 279,
-        ProvideSpellFocus = 280,
-        ModGuildReputationGainPct = 281, // NYI
+        ModArmorPenetrationPct = 280,
+        ProvideSpellFocus = 281,
         ModBaseHealthPct = 282,
         ModHealingReceived = 283,  // Possibly Only For Some Spell Family Class Spells
         Linked = 284,

Source/Game/Entities/Unit/Unit.cs

@@ -3833,11 +3833,14 @@ namespace Game.Entities
                         armor = (float)Math.Floor(MathFunctions.AddPct(ref armor, -eff.GetAmount()));
                 }
 
-                // Apply Player CR_ARMOR_PENETRATION rating
+                // Apply Player CR_ARMOR_PENETRATION rating and buffs from stances\specializations etc.
                 if (attacker.IsPlayer())
                 {
                     float arpPct = attacker.ToPlayer().GetRatingBonusValue(CombatRating.ArmorPenetration);
 
+                    Item weapon = attacker.ToPlayer().GetWeaponForAttack(attackType, true);
+                    arpPct += attacker.GetTotalAuraModifier(AuraType.ModArmorPenetrationPct, aurEff => aurEff.GetSpellInfo().IsItemFitToSpellRequirements(weapon));
+
                     // no more than 100%
                     MathFunctions.RoundToInterval(ref arpPct, 0.0f, 100.0f);