option to remove large "play" button

The large play button used in the updated MaterialControls is covering large part of the video when player is used in a list view widget.

Please add an option to disable/hide this "play" button or give an option to extend/overwrite MaterialControls class to customize controls UI. E.g. make `_buildHitArea()` non-private, or move `CenterPlayButton` creation into a separate non-private method.