Show header for formatter comment decoration info

**Summary** Show a header in the formatter comment decoration debug output that shows which node is preceding/following/enclosing (#6813 (comment)). I also kept this intentionally condensed to make it easy to use this is a small sidebar without vertical scrolling.

```
# Comment decoration: Range Preceding Following Enclosing Comment
1292..1298 Some((ExprName, 1274..1280)) Some((ExprName, 1307..1310)) (StmtAnnAssign, 1274..1316) "# type"
2507..2555 None Some((StmtIf, 2634..2891)) (StmtClassDef, 2478..3279) "# didn't match the name in the C implementation,"
2560..2629 None Some((StmtIf, 2634..2891)) (StmtClassDef, 2478..3279) "# meaning it is only *safe* to pass it as a keyword argument on 3.12+"
3281..3298 Some((StmtClassDef, 2478..3279)) Some((StmtFunctionDef, 3300..3317)) (ModModule, 0..4162) "# Top level rules"
3481..3496 Some((StmtClassDef, 3452..3479)) Some((StmtClassDef, 3498..3876)) (ModModule, 0..4162) "# Nesting rules"
{
    Node {
        kind: ExprName,
        range: 1307..1310,
        source: `int`,
    }: {
...
```

**Test Plan** It's debug output.

crates/ruff_python_formatter/src/cli.rs

@@ -69,6 +69,9 @@ pub fn format_and_debug_print(input: &str, cli: &Cli, source_type: &Path) -> Res
         // Print preceding, following and enclosing nodes
         let source_code = SourceCode::new(input);
         let decorated_comments = collect_comments(&python_ast, source_code, &comment_ranges);
+        if !decorated_comments.is_empty() {
+            println!("# Comment decoration: Range Preceding Following Enclosing Comment");
+        }
         for comment in decorated_comments {
             println!(
                 "{:?} {:?} {:?} {:?} {:?}",