Core/Battlegrounds: Move some areatrigger handling to scripts

Port From (https://github.com/TrinityCore/TrinityCore/commit/9c5b8927f89cda74eb7350801c364b003048ba2b)

Source/Scripts/EasternKingdoms/AlteracValley/AlteracValley.cs

@@ -3,6 +3,7 @@
 
 using Framework.Constants;
 using Game.AI;
+using Game.DataStorage;
 using Game.Entities;
 using Game.Scripting;
 using System;
@@ -134,4 +135,19 @@ namespace Scripts.EasternKingdoms.AlteracValley
                 return;
         }
     }
+
+    [Script]
+    class at_av_exploit : AreaTriggerScript
+    {
+        public at_av_exploit() : base("at_av_exploit") { }
+
+        public override bool OnTrigger(Player player, AreaTriggerRecord trigger)
+        {
+            var battleground = player.GetBattleground();
+            if (battleground != null && battleground.GetStatus() == BattlegroundStatus.WaitJoin)
+                battleground.TeleportPlayerToExploitLocation(player);
+
+            return true;
+        }
+    }
 }