Audio player: show the track info

In cover mode, the screen is empty and we have the place to display the track info as well as other info (Track name / artist, ...)

Design is in progress.

Partially covers #2096 (closed)

changed milestone to %3.4.x

added Android Phone UI feature labels

assigned to @Aza

marked this issue as related to #2096 (closed)

mentioned in merge request !1051 (merged)

closed with commit 7e4f9499