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/window.rs

@@ -1320,6 +1320,11 @@ impl Window {
         self.platform_window.bounds()
     }
 
+    /// Set the content size of the window.
+    pub fn resize(&mut self, size: Size<Pixels>) {
+        self.platform_window.resize(size);
+    }
+
     /// Returns whether or not the window is currently fullscreen
     pub fn is_fullscreen(&self) -> bool {
         self.platform_window.is_fullscreen()