The new X-KWin-Exclusive-Category property is read from the service
and provided to QML through the ExclusiveRole. If an effect has such
a role the CheckBox is replaced by a RadioButton. The radio buttons of
an exclusive group take care that only one effect of the group can be
enabled. In addition the radio button acts like a check box. If one
clicks the checked radio button it gets unchecked.
At the same time this change removes the hard coded functionality for
the exclusive group of desktop switching effects. It's all handled
dynamically by creating the ExclusiveGroup when needed. For each
category there can be one ExclusiveGroup.
REVIEW: 116711
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