desktop-shell: support disallow-output-changed-move

With this, when unplugging an extended display, the view displayed on the extended display won't be re-positioned to other displays.

On some embedded devices, the views are often fullscreen displayed, even on the extended displays. When disconnecting the extended displays, the views are not desired to be moved onto the existing displays. Without this change, we can see the view flash across the existing displays even though the UI process hides the view as soon as it can, which is unexpected.

Signed-off-by: Paul Pu hui.pu@gehealthcare.com