[visionOS] Detect Whether PlayToDevice is Enabled

There’s PolySpatialUserSettings.Instance.ConnectToPlayToDevice, but that only tells you whether the system will attempt to connect to Play to Device when entering play mode in the editor with PolySpatial enabled (i.e., visionOS build target, RealityKit/Hybrid app mode). It won’t tell you whether connection was successful. I think we’ve had requests for that functionality before; if it’s something you’re interested in as well, you could submit it to our road map.