Window: re-aligns all frame handles when the extent changes

necessary when a window's extent is changed programmatically as
it happens when we collapse the navigation of a window,
otherwise the bounds are wrong (and the bounds halo looks wrong)
(full collapsing is handled as a special case in Window>>getBounds)

also, alignAllHandles checks whether the handles are currently
submorphs, which is not true when a window is collapsed (and during
expanding)