Summary:
During the port to Qt5 the circular progress bar was lost, since there is no
simple way to do circular progress bars. Now that KQuickCharts is available
as a framework, we can restore the circular progress bar in the notifications.

Video:
{F7819233}

Test Plan: Start a long-ish running job like copying a file.

Reviewers: #plasma, broulik

Reviewed By: #plasma, broulik

Subscribers: broulik, plasma-devel

Tags: #plasma

Differential Revision: https://phabricator.kde.org/D26012