LibWeb: Move setting of Web object prototypes to initialize()

This needs to happen before prototype/constructor intitialization can be
made lazy. Otherwise, GC could run during the C++ constructor and try to
collect the object currently being created.

Userland/Libraries/LibWeb/HTML/Worker.h

@@ -68,6 +68,7 @@ private:
         return static_cast<Bindings::WebEngineCustomData*>(target_vm.custom_data())->event_loop;
     }
 
+    virtual void initialize(JS::Realm&) override;
     virtual void visit_edges(Cell::Visitor&) override;
 
     DeprecatedFlyString m_script_url;