New label: transition to seen/played

To be in line with the other ports, we should consider chaning the usage of our new label.

Currently, we are displaying this label when a media(video, audio) has never been played before.

For example, on Android the users can manually set a video to "mark as played" or finish the video normally.

For the audio part on Android, this feature isn't used.

Overall by transitionning to the seen/played system, we will uncluster list cells in the interface.