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/session/running/console.rs

@@ -963,8 +963,12 @@ mod tests {
     ) {
         cx.set_state(input);
 
-        let buffer_position =
-            cx.editor(|editor, _, cx| editor.selections.newest::<Point>(cx).start);
+        let buffer_position = cx.editor(|editor, _, cx| {
+            editor
+                .selections
+                .newest::<Point>(&editor.display_snapshot(cx))
+                .start
+        });
 
         let snapshot = &cx.buffer_snapshot();