Split Outline in a composited and non-composited part

The non-composited part handles the showWithX case with the four small
windows. The composited part shows a translucent QWidget with the
FrameSvg as done by the selection effect frame.

Outline connects to the Compositor toggled signal to switch the mode if
compositing gets suspended/resumed. This works fine also in the case that
the switch happens while the outline is shown. To support this Outline
is now a QObject and created with Workspace as a parent.

Given that the Outline handles both cases by itself, the outline effect
is no longer needed and is dropped together with all the hooks into the
effect system.