Core/SAI: Added SAI support for new areatriggers

Port From (https://github.com/TrinityCore/TrinityCore/commit/875fd4107f29c00f148ea77c6ff6d49f7ca92b76)

Source/Game/Entities/AreaTrigger/AreaTrigger.cs

@@ -969,7 +969,7 @@ namespace Game.Entities
             base.ClearUpdateMask(remove);
         }
 
-        AreaTriggerAI GetAI() { return _ai; }
+        public T GetAI<T>() where T : AreaTriggerAI { return (T)_ai; }
 
         public bool IsServerSide() { return _areaTriggerTemplate.Id.IsServerSide; }
 

Source/Game/Entities/AreaTrigger/AreaTriggerTemplate.cs

@@ -192,6 +192,12 @@ namespace Game.Entities
         public uint Id;
         public bool IsServerSide;
 
+        public AreaTriggerId(uint id, bool isServerSide)
+        {
+            Id = id;
+            IsServerSide = isServerSide;
+        }
+
         public override int GetHashCode()
         {
             return Id.GetHashCode() ^ IsServerSide.GetHashCode();

Source/Game/Entities/Creature/Creature.cs

@@ -1540,7 +1540,7 @@ namespace Game.Entities
 
         public override bool CanAlwaysSee(WorldObject obj)
         {
-            if (IsAIEnabled && GetAI().CanSeeAlways(obj))
+            if (IsAIEnabled && GetAI<CreatureAI>().CanSeeAlways(obj))
                 return true;
 
             return false;
@@ -3038,12 +3038,12 @@ namespace Game.Entities
         public bool IsInEvadeMode() { return HasUnitState(UnitState.Evade); }
         public bool IsEvadingAttacks() { return IsInEvadeMode() || CanNotReachTarget(); }
 
-        public new CreatureAI GetAI()
+        public override CreatureAI GetAI()
         {
             return (CreatureAI)i_AI;
         }
 
-        public T GetAI<T>() where T : UnitAI
+        public T GetAI<T>() where T : CreatureAI
         {
             return (T)i_AI;
         }

Source/Game/Entities/GameObject/GameObject.cs

@@ -2779,6 +2779,8 @@ namespace Game.Entities
 
         public GameObjectAI GetAI() { return m_AI; }
 
+        public T GetAI<T>() where T : GameObjectAI { return (T)m_AI; }
+
         public uint GetDisplayId() { return m_gameObjectData.DisplayID; }
 
         public uint GetFaction() { return m_gameObjectData.FactionTemplate; }

Source/Game/Entities/Unit/Unit.cs

@@ -1112,7 +1112,7 @@ namespace Game.Entities
             return m_vehicle != null && m_vehicle == vehicle.GetVehicleKit();
         }
 
-        public UnitAI GetAI() { return i_AI; }
+        public virtual UnitAI GetAI() { return i_AI; }
         public void SetAI(UnitAI newAI) { i_AI = newAI; }
 
         public bool IsPossessing()