Bump to xamarin/Java.Interop/master@be581591 (#3404)

Changes: dotnet/java-interop@4e364ba...be58159

Context: dotnet/java-interop#424

`generator` refactoring.

Make the `*Invoker` classes `partial` classes.

Add `generator --lang-features=interface-constants` option, which
emits Java interface constant values into the C# interface
declarations.

`generator` performance improvements.

Allow consumption of `Java.Interop-Tests` by Xamarin.Android.