gpui: Support window resizing for PlatformWindow (#27477)

Support resizing windows to a specified size.

## macOS

https://github.com/user-attachments/assets/8c639bc2-ee5f-4adc-a850-576dac939574


## Wayland

[wayland.webm](https://github.com/user-attachments/assets/3d593604-83b4-488f-8f63-1cf4c0c0cb9a)

## X11

[x11.webm](https://github.com/user-attachments/assets/ce8fa62e-fb74-4641-abe8-70574011e630)

## Windows

https://github.com/user-attachments/assets/abb03e48-f82a-4d62-90b3-2598a4866c3f

Release Notes:

- N/A

crates/gpui/src/platform.rs

@@ -383,6 +383,7 @@ pub(crate) trait PlatformWindow: HasWindowHandle + HasDisplayHandle {
     fn is_maximized(&self) -> bool;
     fn window_bounds(&self) -> WindowBounds;
     fn content_size(&self) -> Size<Pixels>;
+    fn resize(&mut self, size: Size<Pixels>);
     fn scale_factor(&self) -> f32;
     fn appearance(&self) -> WindowAppearance;
     fn display(&self) -> Option<Rc<dyn PlatformDisplay>>;