X11Extras is not available in QT6 (need to use QNativeInterface::QX11Application)

[neoh4x0r]

The CMakeLists file in QtScrcpy/CMakeLists.txt expects X11Extras to exist in QT6

However, that package existed in QT5 but was removed from qt6.

see https://doc.qt.io/qt-6/extras-changes-qt6.html#changes-to-qt-x11-extras

The Qt X11 Extras module was removed in Qt 6.

For QX11Info::connection(), use QNativeInterface::QX11Application::connection() instead.
For QX11Info::display(), use QNativeInterface::QX11Application::display() instead.
For QX11Info::isPlatformX11(), check QNativeInterface::QX11Application existence instead.