gpui: Make Window::paint_*_shadows pub (#57741)

Self-Review Checklist:

- [x] I've reviewed my own diff for quality, security, and reliability
- [x] Unsafe blocks (if any) have justifying comments
- [x] The content is consistent with the [UI/UX
checklist](https://github.com/zed-industries/zed/blob/main/CONTRIBUTING.md#uiux-checklist)
- [ ] Tests cover the new/changed behavior
- [x] Performance impact has been considered and is acceptable


Release Notes:

- N/A

crates/gpui/src/window.rs

@@ -3454,7 +3454,7 @@ impl Window {
     /// after the element's background so they layer on top of the fill.
     ///
     /// This method should only be called as part of the paint phase of element drawing.
-    pub(crate) fn paint_drop_shadows(
+    pub fn paint_drop_shadows(
         &mut self,
         bounds: Bounds<Pixels>,
         corner_radii: Corners<Pixels>,
@@ -3490,7 +3490,7 @@ impl Window {
     /// Paint the inset shadows from `shadows` into the scene at the current z-index. Should
     /// be called after the element's background so the shadow layers on top of the fill.
     /// Drop shadows are skipped; paint those with [`Self::paint_drop_shadows`] before the background.
-    pub(crate) fn paint_inset_shadows(
+    pub fn paint_inset_shadows(
         &mut self,
         bounds: Bounds<Pixels>,
         corner_radii: Corners<Pixels>,