macosx: Set native full screen mode to on by default

As this is what most macOS users expect from full-screening in media applications, I think we should set this as the default here too. For context -- Safari, QuickTime, and other video player apps use native full screen for videos now.

In our case, it also lets us easily retain the sidebars for the play queue and the navigation if the users want to interact with these during video playback