Context: https://aster.cloud/2021/02/23/lets-be-explicit-about-our-intent-filters/

An important change is coming to Android 12 that improves both app and platform security. This change affects all apps that target Android 12.

Activities, services, and broadcast receivers with declared intent-filters now must explicitly declare whether they should be exported or not.

The short version is that many apps may need to update their [Activity] attribute usage to explicitly set ActivityAttribute.Exported.

However, we added ActivityAttribute.MainLauncher, which is also used in our templates:

https://github.com/xamarin/xamarin-android/blob/f7d32102cc3ada67aa12cc0beed2cf97226f41b3/src/Microsoft.Android.Templates/android/MainActivity.cs#L8

We should update our AndroidManifest.xml generation & related code so that when MainLauncher=true, we also automatically set exported=true.