[kcmkwin/compositing] Remove effect list item selection, fix list item size after hiding the effect video, use a real button as the play button and use the right busy indicator
Summary:
Makes some improvements to the Effects KCM (details in title).
Test Plan: Open the Effects KCM.
Reviewers: KWin, VDG, ngraham, davidedmundson
Reviewed By: KWin, VDG, ngraham, davidedmundson
Subscribers: davidedmundson, ngraham, VDG, kwin, KWin
Differential Revision: https://phabricator.kde.org/D17416