isOptionDisabled method
An option is disabled if the options implements Selectable, but the item
is not selectable.
Implementation
bool isOptionDisabled(T? item) {
// TODO: Verify if this can be simplified to .isDisabledIn.
//
// The prior code did a check for `!= SelectableOption.Selected`. It is
// possible there are existing users that are relying on `.Hidden` to mean
// disabled, for example.
return !Selectable.isSelectableIn(options, item, true);
}