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/mac/window.rs

@@ -805,6 +805,21 @@ impl PlatformWindow for MacWindow {
         self.0.as_ref().lock().content_size()
     }
 
+    fn resize(&mut self, size: Size<Pixels>) {
+        let this = self.0.lock();
+        let window = this.native_window;
+        this.executor
+            .spawn(async move {
+                unsafe {
+                    window.setContentSize_(NSSize {
+                        width: size.width.0 as f64,
+                        height: size.height.0 as f64,
+                    });
+                }
+            })
+            .detach();
+    }
+
     fn scale_factor(&self) -> f32 {
         self.0.as_ref().lock().scale_factor()
     }