vulkan/wsi/x11: report device-group present rectangles with prime.

dEQP-VK.wsi.xlib.surface.query_devgroup_present_modes with prime fail when 0 rectangles are reported. While I believe that test tests this unintentionally (trying to test the VK_INCOMPLETE return), I believe it makes sense to always return a rectangle.

In particular we require the data from the given rectangle for presentation even if we use prime and given that prime is completely transparent for the app it still counts as local from the perspective as the application.