Expose MediaElement's native view for player customization beyond what MediaElement supports

[philipag]

A public object getter for the native view (Android => AndroidX.Media3.UI.PlayerView, iOS => AVPlayerViewController, etc.) would simplify native customization that goes beyond what MediaElement supports.

Some functions like showing/hiding the media controls are too different between platforms and instead of trying to add the functionality to MediaElement, exposing the underlying object will make it easy to customize without having to add a lot of boiler plate.

Customiztion examples:

iOS:

playerView.SetValueForKey(Foundation.NSObject.FromObject(false), (Foundation.NSString)"canHidePlaybackControls");
playerView.SetValueForKey(Foundation.NSObject.FromObject(true), (Foundation.NSString)"entersFullScreenWhenPlaybackBegins");
playerView.SetValueForKey(Foundation.NSObject.FromObject(true), (Foundation.NSString)"showsExitFullScreenButton");
playerView.SetValueForKey(Foundation.NSObject.FromObject(true), (Foundation.NSString)"exitsFullScreenWhenPlaybackEnds");
playerView.SetValueForKey(Foundation.NSObject.FromObject(true), (Foundation.NSString)"showsMinimalPlaybackControlsWhenEmbeddedInline");

Android:

playerView.ControllerHideOnTouch = false;
playerView.ControllerShowTimeoutMs = 0;
playerView.ShowController();

[philipag]

In addition to the view, it would probably makes sense to create a getter for the Player object (e.g. iOS AVFoundation.AVPlayer) since that can be used for further customization in some scenarios.