the intent of these hacks was to break cyclic references to avoid having objects lingering in memory. However, all of the stuff that's being removed in this commit no longer has any effect anyway, due to the fact that these things don't circularly reference each other anymore. Notably, Tile inventories now keep Position instead of a Tile ref.
now, EnderChestInventory is just a temporary window, much like anvil/enchanting windows. It provides a gateway to the player's PlayerEnderInventory.
This removes one of the remaining obstacles to disallowing null World in Position constructor.
