Extend the "loading" animation in the listen screen

[SyntaxBlitz]

In between the track loading and the track auto-playing on the listen screen, there's a period where the "play" button shows. This isn't ideal, since we're about to auto-play the track anyway (it also just kind of looks bad to have all that 'flickering'). We should figure out when we're truly waiting for the user to press the play button (in which case we should render a play button) versus when we're waiting on the track to autoplay (in which case we should keep showing the ActivityIndicator).