Maintain smooth frame rates when ProMotion and direct mode are enabled (#7305)

This is achieved by starting a `CADisplayLink` that will invoke the
`on_request_frame` callback at the refresh interval of the display.

We only actually draw frames when the window was dirty, or for 2 extra
seconds after the last input event to ensure ProMotion doesn't downclock
the refresh rate when the user is actively interacting with the window.

Release Notes:

- Improved performance when using a ProMotion display with fast key
repeat rates.

---------

Co-authored-by: Nathan Sobo <nathan@zed.dev>

crates/gpui/src/platform.rs

@@ -175,7 +175,6 @@ pub(crate) trait PlatformWindow: HasWindowHandle + HasDisplayHandle {
     fn on_close(&self, callback: Box<dyn FnOnce()>);
     fn on_appearance_changed(&self, callback: Box<dyn FnMut()>);
     fn is_topmost_for_position(&self, position: Point<Pixels>) -> bool;
-    fn invalidate(&self);
     fn draw(&self, scene: &Scene);
 
     fn sprite_atlas(&self) -> Arc<dyn PlatformAtlas>;