Deprecate values_trait in ButtonEditor?

The Qt implementation of the *simple* `ButtonEditor` takes into account of the `values_trait` in the editor factory:
https://github.com/enthought/traitsui/blob/25e6f83aec9c483b189ec43037440dd71bc4745d/traitsui/editors/button_editor.py#L53-L57

The user manual says more or less the same thing:
> Use values_trait to specify the name of the trait on the object that contains the list of possible values. If this is set, then the value, label, and label_value traits are ignored; instead, they will be set from this list. When this button is clicked, the value set will be the one selected from the drop-down.

But there are no implementations for this trait in wx `ButtonEditor` or the custom version of qt `ButtonEditor`. I also could not work out how this is supposed to work: I got as far as getting a button but there is no drop-down. The description of this trait also looks similar to what `EnumEditor` does.

All these signs point to this question: Can we deprecate `values_trait` on `ButtonEditor` instead of trying to fix/maintain it?