LibWeb: Move use pseudo element styles from TreeBuilder to StyleComputer

The styling of elements using the `use_pseudo_element()` was only
applied on layout. When an element style was recomputed later that
styling was not overruled with the pseudo element selector styles.
This moves the styling override from `TreeBuilder.cpp` to
`StyleComputer.cpp`. Now the styles are always correctly applied.
I also removed the method `property_id_by_index()` because it was
not needed anymore.

Als some calls to `invalidate_layout()` in the Meter, Progress and
Select elements where not needed anymore because the style values
are update on the changing of the style attribute.

This fixes issue #22278.

Userland/Libraries/LibWeb/CSS/ResolvedCSSStyleDeclaration.h

@@ -21,7 +21,6 @@ public:
 
     virtual size_t length() const override;
     virtual String item(size_t index) const override;
-    virtual CSS::PropertyID property_id_by_index(size_t index) const override;
 
     virtual Optional<StyleProperty> property(PropertyID) const override;
     virtual WebIDL::ExceptionOr<void> set_property(PropertyID, StringView css_text, StringView priority) override;