Make better code structure for border handlers

Sine Striker

2023-12-13 a51b5688e1c33d3ce96b48c869603b00f908f513

 src/widgets/widgetwindowagent_p.h

@@ -17,7 +17,9 @@
        // Host
        QWidget *hostWidget{};

        std::unique_ptr<QObject> paintFilter;
#ifdef Q_OS_WINDOWS
        void setupWindows10BorderWorkaround();
#endif
    };

}