Needs to implement a dummy switcher item. As the root item of the
switchers are no longer QQuickItem derived it cannot use a QQuickView.
Instead a component gets created and the switcher is just shown on the
primary screen. It's a more appropriate preview now which is not
put into a dialog window.
To make it more realistic (and to be able to dismiss it) the preview
grabs keyboard and mouse and closes itself if escape, return, enter or
space is pressed.
As well clicking outside the preview window closes the preview.
Next to the preview/configure button a GHNS button is included
as a simple button with icon only to not break the layout.
Currently the button is not shown as the category on kde-look
has not yet been created yet.
CCBUG: 297636
REVIEW: 104894
