Apparently useful in modding workflows when you want to test out a few
different variants of a thing.
Re-uses `Ctrl-L` binding from stable. Some folks may argue that the
dialog makes the hotkey pointless, but I really do want to protect
users from accidental data loss, and also if you want to power through
it quickly, you can hit the 1 key when the dialog shows, which will
bypass the hold-to-activate period (which wasn't intentional, but so
many people want a bypass at this point that we're probably keeping that
behaviour for power users).
To be hoenst, this is all quite abusive but I'm not sure how to do it in
any better way. I especially dislike the fact that the screen's
bindables are disabled yet the screen itself is allowed to set their
value because they're `LeasedBindable`s.
But I feel better doing this in a central location like this
`ScreenStack` than in the rooms... Otherwise this specific behaviour
would have to be replicated in the multiplayer screen when it goes
through the same refactoring.