Synthesize a mouse moved event in the previous position after painting a scene

This ensures that we correctly update the hover state of elements whose position has changed relative to the mouse cursor even though the mouse hasn't actually moved.

Co-Authored-By: Antonio Scandurra <me@as-cii.com>
Co-Authored-By: Max Brunsfeld <maxbrunsfeld@gmail.com>

gpui/src/platform/event.rs

@@ -1,6 +1,6 @@
 use crate::{geometry::vector::Vector2F, keymap::Keystroke};
 
-#[derive(Debug)]
+#[derive(Clone, Debug)]
 pub enum Event {
     KeyDown {
         keystroke: Keystroke,