[kde] clean up overlay and use Matcha-Dark theme

overlays/kde/etc/sddm.conf

overlays/kde/etc/skel/.config/akregatorrc

overlays/kde/etc/skel/.config/baloofileinformationrc

overlays/kde/etc/skel/.config/baloofilerc

overlays/kde/etc/skel/.config/bluedevilglobalrc

overlays/kde/etc/skel/.config/gtk-3.0/settings.ini

overlays/kde/etc/skel/.config/gwenviewrc

overlays/kde/etc/skel/.config/kateschemarc

overlays/kde/etc/skel/.config/kcmdisplayrc

overlays/kde/etc/skel/.config/kconf_updaterc

overlays/kde/etc/skel/.config/kded_device_automounterrc

overlays/kde/etc/skel/.config/kdeglobals

overlays/kde/etc/skel/.config/kinfocenterrc

overlays/kde/etc/skel/.config/kscreenlockerrc

overlays/kde/etc/skel/.config/ksplashrc

overlays/kde/etc/skel/.config/ksysguardrc

overlays/kde/etc/skel/.config/ktimezonedrc

overlays/kde/etc/skel/.config/kwinrc

overlays/kde/etc/skel/.config/libaccounts-glib/accounts.db

...ays/kde/etc/skel/.config/libaccounts-glib/accounts.db-shm