Add BusyIndicator to the styled controls list

Summary:

• Use breeze view-refresh icon
• Use appear/fade animation

I'm not sure what can be improved here tbh, any suggestions are welcome.
Qt 5.10 includes PathArc that could make rotation more smooth and
remove breeze icon dependency but for now that's all I managed to do.

Reviewers: mart

Reviewed By: mart

Differential Revision: https://phabricator.kde.org/D9804