Expand diagnostic excerpts using heuristics on syntactic information from TreeSitter (#21942)

This is quite experimental and untested in languages other than Rust.
It's written to attempt to do something sensible in many languages. Due
to its experimental nature, just releasing to staff, and so not
including it in release notes. Future release note might be "Improved
diagnostic excerpts by using syntactic info to determine the context
lines to show."

Release Notes:

- N/A

crates/editor/src/editor.rs

@@ -8774,9 +8774,10 @@ impl Editor {
             .map(|selection| {
                 let old_range = selection.start..selection.end;
                 let mut new_range = old_range.clone();
-                while let Some(containing_range) =
-                    buffer.range_for_syntax_ancestor(new_range.clone())
+                let mut new_node = None;
+                while let Some((node, containing_range)) = buffer.syntax_ancestor(new_range.clone())
                 {
+                    new_node = Some(node);
                     new_range = containing_range;
                     if !display_map.intersects_fold(new_range.start)
                         && !display_map.intersects_fold(new_range.end)
@@ -8785,6 +8786,17 @@ impl Editor {
                     }
                 }
 
+                if let Some(node) = new_node {
+                    // Log the ancestor, to support using this action as a way to explore TreeSitter
+                    // nodes. Parent and grandparent are also logged because this operation will not
+                    // visit nodes that have the same range as their parent.
+                    log::info!("Node: {node:?}");
+                    let parent = node.parent();
+                    log::info!("Parent: {parent:?}");
+                    let grandparent = parent.and_then(|x| x.parent());
+                    log::info!("Grandparent: {grandparent:?}");
+                }
+
                 selected_larger_node |= new_range != old_range;
                 Selection {
                     id: selection.id,