AudioPlayer: Adjust play queue behavior

This merge request brings an adjustment and a fix to the audio player's play queue behavior:

• The play queue view is not removed from the parent view controller when the mini player is discarded anymore.
• The view is instead removed before adding it to the mini player to avoid conficts with its possible parents.
• The play queue is not hidden when the player enters its full screen mode in order to avoid any conflict with the player's play queue display.
• The play queue is hidden when the audio player view disappears.

Closes #1682 (closed)