Fix issues where screen and window sizes contained Pixels, but were declared as DevicePixels (#12991)

On most platforms, things were working correctly, but had the wrong
type. On X11, there were some problems with window and display size
calculations.

Release Notes:

- Fixed issues with window positioning on X11

---------

Co-authored-by: Conrad Irwin <conrad.irwin@gmail.com>
Co-authored-by: Mikayla <mikayla@zed.dev>

crates/gpui/examples/image/image.rs

@@ -80,8 +80,8 @@ fn main() {
             }),
 
             window_bounds: Some(WindowBounds::Windowed(Bounds {
-                size: size(px(1100.), px(600.)).into(),
-                origin: Point::new(DevicePixels::from(200), DevicePixels::from(200)),
+                size: size(px(1100.), px(600.)),
+                origin: Point::new(px(200.), px(200.)),
             })),
 
             ..Default::default()