utils/xcbutils: Use window geometry in device pixels

If the logical geometry changes, the X11Window still needs to verify whether the currently applied native geometry differs from it. In order to do that, the X11Window needs to map the logical geometry to the device pixels. Given that X11Window already maps the logical pixels to the device pixels, the Xcb::Window doesn't need to map the geometry again.

Also, the way different coordinate spaces are handled now is inconsistent. Some things (Xcb::Window) work only with the logical pixels, while other (e.g. client messages) require the user manually mapping the geometry between the different coordinate spaces. With this change, it would be more consistent.