Allow setting iOS status bar visibility without being tied to full screen

[KyleHershey]

Intent

The current implementation of PrefersStatusBarHidden on iOS is based on IsFullScreen in GraphicsDeviceManager. This is fine, but setting IsFullScreen to true has other consequences like needing to swipe up twice to exit the app. Developers should be able to have more granular control over whether they want to hide the status bar, but not have the other consequences of being a full screen app.

Implementation here:

MonoGame/MonoGame.Framework/Platform/iOS/iOSGameViewController.cs

Lines 111 to 114 in 39313ed

	public override bool PrefersStatusBarHidden()
	{
	return _platform.Game.graphicsDeviceManager.IsFullScreen;
	}

Motivation

I'm doing this by forking MonoGame, but shouldn't have to do this: there should be something like an Info.plist entry which can be toggled on/off to toggle the status bar (and if not present use the default implementation), or a boolean in the Game class, etc.