create a FlatButtonWithToolTip component for MediaPlayerControl

Summary:
Factors out the code of MediaPlayerControl to a button component so that the code is reused
and make it compatible with qqc2 actions
T7576

Reviewers: mgallien, januz

Reviewed By: mgallien

Tags: Elisa

Differential Revision: https://phabricator.kde.org/D13872