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/language_tools/src/syntax_tree_view.rs

@@ -252,7 +252,10 @@ impl SyntaxTreeView {
             .editor
             .update(cx, |editor, cx| editor.snapshot(window, cx));
         let (buffer, range, excerpt_id) = editor_state.editor.update(cx, |editor, cx| {
-            let selection_range = editor.selections.last::<usize>(cx).range();
+            let selection_range = editor
+                .selections
+                .last::<usize>(&editor.display_snapshot(cx))
+                .range();
             let multi_buffer = editor.buffer().read(cx);
             let (buffer, range, excerpt_id) = snapshot
                 .buffer_snapshot()