fix(Core): Instance Reset Exploit Fix (#12459)

* fix(Core): Fix Instance Reset Exploit

* Whitespace fix

* Remove unnecessary include

* Check player instance save IDs when adding to map

* Only compare playerBind during login

src/server/game/Maps/Map.cpp

@@ -2959,6 +2959,11 @@ bool InstanceMap::AddPlayerToMap(Player* player)
                 return false;
             }
         }
+        else if (player->GetSession()->PlayerLoading() && playerBind && playerBind->save != mapSave)
+        {
+            // Prevent "Convert to Raid" exploit to reset instances
+            return false;
+        }
         else
         {
             playerBind = sInstanceSaveMgr->PlayerBindToInstance(player->GetGUID(), mapSave, false, player);