no longer have a play icon bouncing but use an icon like the plasma taskbar

Summary:
no longer have a play icon bouncing but use an icon like the plasma taskbar

We no longer have an animation running when music is playing. We should no longer have excess cpu usage.

We now use a common icon to indicate the playing track (plasma task bar, firefox tabs, ...)

Test Plan: cpu usage should be lower when playing music

Reviewers: Elisa, VDG, astippich

Reviewed By: Elisa, astippich

Subscribers: romangg, astippich

Differential Revision: https://phabricator.kde.org/D11667