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/debugger_ui/src/stack_trace_view.rs

@@ -55,7 +55,10 @@ impl StackTraceView {
         cx.subscribe_in(&editor, window, |this, editor, event, window, cx| {
             if let EditorEvent::SelectionsChanged { local: true } = event {
                 let excerpt_id = editor.update(cx, |editor, cx| {
-                    let position: Point = editor.selections.newest(cx).head();
+                    let position: Point = editor
+                        .selections
+                        .newest(&editor.display_snapshot(cx))
+                        .head();
 
                     editor
                         .snapshot(window, cx)