Blank splash screens on iOS 16.5+ simulators

[davidbritch]

The splash screen on iOS simulators are sometimes black if you are not using a developer certificate. Splash screens will still appear on older simulators (such as iOS 15.5) or if you are doing a release build.

The simulator won't load launch screens unless the app is signed. Therefore you must enable codesigning in simulator builds as a workaround.

https://github.com/xamarin/xamarin-macios/issues/18469