Allow copying current track details by clicking.

With text copying from QML Labels being surprisingly hard (https://bugreports.qt.io/browse/QTBUG-14077), this might be the cleanest way to implement at least some kind of copy functionality. The functionality is not completely obvious, but pointer cursor should help a little bit. Some kind of "copied to clipboard" animation or confirmation text would be better, but would require a new string, so won't come just now.

BUG: 283457