Switch/toggle input type

[vadosnaprimer]

We have bool buttons and analog, but they both reset their state to default (false for buttons and mid for analog) after you've changed them once.

For certain things we need a way to switch between on/off or a different number of variations, in a way that makes the last changed state persist until it's changed again.

#2048 contains a lot of context, and #3757 is an example when it's needed.

Yoshi suggested this

We might be able to add "is sticky" semantics to AxisSpec, or maybe Controller needs to change.

and I think the former is a good idea, but I wonder if there are cases when analog numbers would not be sufficient for such a switch, because how would a user know what the values mean?