Fix a few regressions related to the flicker fix (#9190)

This pull request fixes
https://github.com/zed-industries/zed/issues/9187 and fixes also ix a
rendering problem that would show cursors on the same plane:


![image](https://github.com/zed-industries/zed/assets/482957/208304a4-286a-4fd9-a3d8-e2913e3a3dc7)


Release Notes:

- N/A

crates/editor/src/element.rs

@@ -2083,11 +2083,9 @@ impl EditorElement {
     }
 
     fn paint_cursors(&mut self, layout: &mut EditorLayout, cx: &mut ElementContext) {
-        cx.paint_layer(layout.text_hitbox.bounds, |cx| {
         for cursor in &mut layout.cursors {
             cursor.paint(layout.content_origin, cx);
         }
-        });
     }
 
     fn paint_scrollbar(&mut self, layout: &mut EditorLayout, cx: &mut ElementContext) {

crates/workspace/src/modal_layer.rs

@@ -139,7 +139,13 @@ impl Render for ModalLayer {
             return div();
         };
 
-        div().absolute().size_full().top_0().left_0().child(
+        div()
+            .occlude()
+            .absolute()
+            .size_full()
+            .top_0()
+            .left_0()
+            .child(
                 v_flex()
                     .h(px(0.0))
                     .top_20()