When the choice_loader is built-in / out of scope, working with the choices can be a real pain. As such i'd like to recall for #21717 / #22136

Given

$form = $this->createForm(TimezoneType::class, null, [
    'intl' => true,
    'group_by' => function ($tz) {
        return Timezones::getGmtOffset($tz);
    },
]);

The UX is completely off due default ordering;

Perhaps this should be solved per type, but i tend to believe having some generic solution is nice. Or maybe there's a better way?

Moreover, as we deprecated the region/zone option; there's currently no sane alternative to apply such a filter. Consider #28624 for this :)