Fixes: #802

For interfaces that contain static consts or other members that traditionally could not be placed in a C# interface we create an abstract class with an internal constructor that contains the members so users could access them. However, we place a [Register] on them that points to the original interface. This can cause problems when trying to resolve Java -> C# types, as multiple C# types [Register] the same Java type:

[Register ("android/provider/BaseColumns", DoNotGenerateAcw=true)] 
public abstract class BaseColumns : Java.Lang.Object { ... }

[Register ("android/provider/BaseColumns", DoNotGenerateAcw=true)] 
public abstract class BaseColumnsConsts : IBaseColumns { ... }

[Register ("android/provider/BaseColumns", "", "android.provider.IBaseColumnsInvoker")] 
public interface IBaseColumns { ... }

We tried to remove these [Register] attributes by default, but then JCWs would get generated for them as they inherit JLO and no longer had DoNotGenerateAcw. Instead, we will place them in a dummy package (mono/internal/etc) so that any user that finds them will get a hint that they are "internal" details. (Note that we will never actually generate the JCW files because of DoNotGenerateAcw.)

[Register ("mono/internal/android/provider/BaseColumns", DoNotGenerateAcw=true)] 
public abstract class BaseColumns : Java.Lang.Object { ... }

[Register ("mono/internal/android/provider/BaseColumns", DoNotGenerateAcw=true)] 
public abstract class BaseColumnsConsts : IBaseColumns { ... }

dotnet/android test PR: dotnet/android#9196