AllocWithOptionsPayload

fn AllocWithOptionsPayload(comptime Elem: type, comptime alignment: ?Alignment, comptime sentinel: ?Elem) type {
    if (sentinel) |s| {
        return [:s]align(if (alignment) |a| a.toByteUnits() else @alignOf(Elem)) Elem;
    } else {
        return []align(if (alignment) |a| a.toByteUnits() else @alignOf(Elem)) Elem;
    }
}