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/helix/duplicate.rs

@@ -56,7 +56,8 @@ impl Vim {
         let times = times.unwrap_or(1);
         self.update_editor(cx, |_, editor, cx| {
             let mut selections = Vec::new();
-            let (map, mut original_selections) = editor.selections.all_display(cx);
+            let map = editor.display_snapshot(cx);
+            let mut original_selections = editor.selections.all_display(&map);
             // The order matters, because it is recorded when the selections are added.
             if above {
                 original_selections.reverse();

crates/vim/src/helix/paste.rs

@@ -44,7 +44,8 @@ impl Vim {
                     return;
                 };
 
-                let (display_map, current_selections) = editor.selections.all_adjusted_display(cx);
+                let display_map = editor.display_snapshot(cx);
+                let current_selections = editor.selections.all_adjusted_display(&display_map);
 
                 // The clipboard can have multiple selections, and there can
                 // be multiple selections. Helix zips them together, so the first