Reduce display_map snapshot creation (#39354)

Re-applies https://github.com/zed-industries/zed/pull/30840

This PR re-applies the initial
[PR](https://github.com/zed-industries/zed/pull/30840). As it was closed
because it was hard to land, because of the many conflicts. This PR
re-applies the changes for it.

In several cases we were creating multiple display_map
snapshots within the same root-level function call.
Creating a display_map snapshot is quite slow, and in some
cases we were creating the snapshot multiple times.

Release Notes:

- N/A

crates/vim/src/test.rs

@@ -2295,7 +2295,10 @@ async fn test_clipping_on_mode_change(cx: &mut gpui::TestAppContext) {
 
     let mut pixel_position = cx.update_editor(|editor, window, cx| {
         let snapshot = editor.snapshot(window, cx);
-        let current_head = editor.selections.newest_display(cx).end;
+        let current_head = editor
+            .selections
+            .newest_display(&snapshot.display_snapshot)
+            .end;
         editor.last_bounds().unwrap().origin
             + editor
                 .display_to_pixel_point(current_head, &snapshot, window)