Add Mac system button area interfaces

Sine Striker

2023-12-17 52a662ed17db6c3a3ff2050d61bc2e06ea21b056

 src/widgets/widgetwindowagent_p.h

@@ -16,6 +16,10 @@

        // Host
        QWidget *hostWidget{};
#ifdef Q_OS_MAC
        QWidget *systemButtonAreaWidget{};
        std::unique_ptr<QObject> systemButtonAreaWidgetEventFilter;
#endif

#ifdef Q_OS_WINDOWS
        void setupWindows10BorderWorkaround();