devtools: Allow highlighting elements from the inspector (#35822)

This change connects the `HighlighterActor` from the devtools with the
document, which will draw a blue rectangle over any highlighted dom
node.



https://github.com/user-attachments/assets/571b2dab-497f-4102-9e55-517cdcc040ba




---
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- [X] `./mach build -d` does not report any errors
- [X] `./mach test-tidy` does not report any errors
- [X] These changes do not require tests because we don't have devtools
tests

Signed-off-by: Simon Wülker <simon.wuelker@arcor.de>

components/layout/layout_impl.rs

@@ -651,6 +651,7 @@ impl LayoutThread {
             ))),
             iframe_sizes: Mutex::default(),
             use_rayon: rayon_pool.is_some(),
+            highlighted_dom_node: reflow_request.highlighted_dom_node,
         };
 
         self.restyle_and_build_trees(