Core/Spells: fix wrong distance calculations in AoE spells

Port From (https://github.com/TrinityCore/TrinityCore/commit/5d076cfe291980bc5be9d44ffbae887e3dd5ad59)

Source/Game/Entities/Object/Position.cs

@@ -271,6 +271,13 @@ namespace Game.Entities
 
             return true;
         }
+
+        public bool IsWithinDoubleVerticalCylinder(Position center, float radius, float height)
+        {
+            float verticalDelta = GetPositionZ() - center.GetPositionZ();
+            return IsInDist2d(center, radius) && Math.Abs(verticalDelta) <= height;
+        }
+        
         public bool HasInArc(float arc, Position obj, float border = 2.0f)
         {
             // always have self in arc