Fixup OTP issues around fullscreen/focused windows with transients.
Because of the focus status changes implicitly changing the OTP layer, we have to move the window and all its transients in the OWL stack. However, existing code didn't try to move them all, and even if it did, it made assumptions about how to find them that aren't exactly valid. Instead, change over to explicit functions for the un/focus handling of focus-sensitive windows that know the facts of that and the innards of OTP, rather than trying to use the generic restack functionality.
This is probably not the best solution, and may be reworked. However, it's pretty uninvasive, so is well positioned for backporting as desirable.