gdkwindow: configure native windows in move_native_children()

gdkwindow: configure native windows in move_native_children()

ClutterEmbed on Wayland uses a subsurface and relocates it on configure
events, but when placed within a scrolled window, no configure event is
emitted and the ClutterEmbed subsurface remains static.

Emit a configure event for native windows in GdkWindow's internal
move_native_children() so that custom widgets relying on configure
events such as ClutterEmbed can relocate their stuff.

Similarly, when switching to/from normal/maximized/fullscreen states
which change the shadows' size and possibly shows/hides a header bar,
we need to emit a configure event even if the abs_x/abs_y haven't
changed to make sure the subsurface is size appropriately.

https://bugzilla.gnome.org/show_bug.cgi?id=771320
https://bugzilla.gnome.org/show_bug.cgi?id=767713