LibWeb: Avoid many style invalidations on DOM attribute mutation

Many times, attribute mutation doesn't necessitate a full style
invalidation on the element. However, the conditions are pretty
elaborate, so this first version has a lot of false positives.

We only need to invalidate style when any of these things apply:

1. The change may affect the match state of a selector somewhere.
2. The change may affect presentational hints applied to the element.

For (1) in this first version, we have a fixed list of attribute names
that may affect selectors. We also collect all names referenced by
attribute selectors anywhere in the document.

For (2), we add a new Element::is_presentational_hint() virtual that
tells us whether a given attribute name is a presentational hint.

This drastically reduces style work on many websites. As an example,
https://cnn.com/ is once again browseable.

Libraries/LibWeb/HTML/HTMLTableCellElement.h

@@ -34,6 +34,7 @@ private:
     virtual bool is_html_table_cell_element() const override { return true; }
 
     virtual void initialize(JS::Realm&) override;
+    virtual bool is_presentational_hint(FlyString const&) const override;
     virtual void apply_presentational_hints(GC::Ref<CSS::CascadedProperties>) const override;
 };