use KBusyIndicatorWidget for all busy indication uses
Summary:
unlike the pixmapsequence this scales properly and is actually theme color
sensitive (contrast on dark themes) and looks nicely integrated into plasma
Test Plan: triggered all possible busy indicators and they look dandy
Reviewers: Plasma, broulik
Reviewed By: Plasma, broulik
Subscribers: plasma-devel
Tags: Plasma
Differential Revision: https://phabricator.kde.org/D24158