gpui: Unify track_scroll method to receive a reference type (#43518)

Release Notes:

- N/A

This PR to change the `track_scroll` method to receive a reference type
like the
[Div#track_scroll](https://docs.rs/gpui/latest/gpui/trait.StatefulInteractiveElement.html#method.track_scroll),
[Div#track_focus](https://docs.rs/gpui/latest/gpui/trait.InteractiveElement.html#method.track_focus).


```diff
- .track_scroll(self.scroll_handle.clone())
+ .track_scroll(&self.scroll_handle)

- .vertical_scrollbar_for(self.scroll_handle.clone(), window, cx)
+ .vertical_scrollbar_for(&self.scroll_handle, window, cx)
```


https://github.com/zed-industries/zed/blob/56a2f9cfcf0c6a3c38f596b58002953763cd890f/crates/gpui/src/elements/div.rs#L1088-L1093


https://github.com/zed-industries/zed/blob/56a2f9cfcf0c6a3c38f596b58002953763cd890f/crates/gpui/src/elements/div.rs#L613-L620

crates/git_ui/src/git_panel.rs

@@ -3939,7 +3939,7 @@ impl GitPanel {
                             ListHorizontalSizingBehavior::Unconstrained,
                         )
                         .with_width_from_item(self.max_width_item_index)
-                        .track_scroll(self.scroll_handle.clone()),
+                        .track_scroll(&self.scroll_handle),
                     )
                     .on_mouse_down(
                         MouseButton::Right,
@@ -3949,7 +3949,7 @@ impl GitPanel {
                     )
                     .custom_scrollbars(
                         Scrollbars::for_settings::<GitPanelSettings>()
-                            .tracked_scroll_handle(self.scroll_handle.clone())
+                            .tracked_scroll_handle(&self.scroll_handle)
                             .with_track_along(
                                 ScrollAxes::Horizontal,
                                 cx.theme().colors().panel_background,