Player.EmptySlot and PhotonNetwork.InstantiateItemRoom each gained an
optional parameter, which compiles fine but left the previous build
calling signatures that no longer exist. The InstantiateItemRoom throw
escaped the BagsForEveryone postfix and took down every
SingleItemSpawner in the level, which is why backpacks and BingBong
stopped spawning and campfires no longer advanced the biome.
Also hardens that postfix so a future API change costs the extra bags
and nothing else, registers them with the spawner's SpawnedItemTracker,
and stops the Open Backpack keybind from opening the wheel while the
backpack is held in hand.
