Core/Spells: Implemented evoker empower spell mechanic

Port From (https://github.com/TrinityCore/TrinityCore/commit/a39d0db9ec64f6bf38716abaade5b7835f2db338)

Source/Framework/Constants/ScriptsConst.cs

@@ -34,7 +34,9 @@ namespace Framework.Constants
         CalcDamage,
         CalcHealing,
         OnPrecast,
-        CalcCastTime
+        CalcCastTime,
+        EmpowerStageCompleted,
+        EmpowerCompleted
     }
 
     // AuraScript interface - enum used for runtime checks of script function calls

Source/Framework/Constants/Spells/SpellConst.cs

@@ -26,6 +26,9 @@ namespace Framework.Constants
 
         public const uint VisualKitFood = 406;
         public const uint VisualKitDrink = 438;
+
+        public const uint EmpowerHoldTimeAtMax = 1 * Time.InMilliseconds;
+        public const uint EmpowerHardcodedGCD = 359115;
     }