Add support for PrefersNonDefaultGPU desktop key
This is a standard key which should replace X-KDE-RunOnDiscreteGpu. https://specifications.freedesktop.org/desktop-entry-spec/desktop-entry-spec-latest.html#recognized-keys
This is a standard key which should replace X-KDE-RunOnDiscreteGpu. https://specifications.freedesktop.org/desktop-entry-spec/desktop-entry-spec-latest.html#recognized-keys