Pass a desktopfile name to kcmshell5
Summary:
In order to have a proper window icon for kcmshell5 on Wayland KWin
needs to pass a desktop file name as command line argument.
The desktop file of kwinfocus is used as it uses the
preferences-system-windows icon which is also the icon on X11.
Reviewers: KWin, Plasma on Wayland
Subscribers: plasma-devel, kwin
Tags: Plasma on Wayland, KWin
Differential Revision: https://phabricator.kde.org/D3162