World Subsystem used to react to level and world changes. When Concert reloads the packages, streamed levels are removed and re-added without invoiking LoadMap which circumvents FDisplayClusterGameManager::StartScene method invoked inside LoadMap method of DisplayClusterGameEngine. This causes issues such as not updating references to DisplayClusterRootActor which causes memory corruption, crashes and graphic corruption. This Subsystem is used to react to changes in number of levels used in the current world and forces DisplayClusterModule to refresh all of its managers.