LibWeb: Support RadioNodeList named items in HTMLFormControlsCollection

We would previously not return a RadioNodeList in the curious case where
a named item resolves to two different elements within the form.

This was not a problem when calling namedItem directly in the IDL as
named_item_or_radio_node_list shadows named_item but is exposed when
calling the property through array bracket notation (as an example).

Fix this, and add a bunch more tests to cover
HTMLFormControlsCollection.

Userland/Libraries/LibWeb/DOM/HTMLFormControlsCollection.h

@@ -25,6 +25,8 @@ public:
 protected:
     virtual void initialize(JS::Realm&) override;
 
+    virtual WebIDL::ExceptionOr<JS::Value> named_item_value(FlyString const& name) const final;
+
 private:
     HTMLFormControlsCollection(ParentNode& root, Scope, Function<bool(Element const&)> filter);
 };