[effects] Move Fade, Glide, and Scale effect into exclusive group
Summary:
Fade, glide, and scale effect are mutually exclusive effects so they have
to be put into an exclusive group in the desktop effects kcm.
Test Plan:
Reviewers: KWin, Plasma, VDG, ngraham, graesslin
Reviewed By: KWin, Plasma, VDG, ngraham, graesslin
Subscribers: kwin
Tags: KWin
Differential Revision: https://phabricator.kde.org/D16858