qpa: Provide a QPlatformNativeInterface

Under Gnome/Unity/XFCE, but not Plasma(!), QFontconfigDatabase queries the platform native interface for certain font settings (e.g. antialiasingEnabled). Without a QPNI this would crash KWin as soon as it tried to query for fonts.

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Fixes running nested kwin_wayland in a Gnome/Budgie/etc session.

For the reference, Qt code that triggered this: https://code.woboq.org/qt5/qtbase/src/platformsupport/fontdatabases/fontconfig/qfontconfigdatabase.cpp.html#922

Kai Uwe Broulik kai_uwe.broulik@mbition.io on behalf of MBition GmbH

https://github.com/mercedes-benz/daimler-foss/blob/master/PROVIDER_INFORMATION.md