UI: Canister to be always an option for priority

Hi,

Canisters should be generally available as a choice for priority of any treatment room. Not just once they spawn. Best be its own button to just switch on or off to not be hidden in the disease-list. It should still take up a priority slot (though I don't think I ever needed more than one anyway).

If it's not a disease that has been come across/diagnosed yet, that's fine, but canisters are standard objective goals. More like an industrial thing.