[XAT.Bytecode] Fix issue where Kotlin public types inside internal types were not being hidden.

[jpobst]

Fixes: #826
Context: #682

Given the following Kotlin code:

internal MyClass {
  public MyInterface { }
}

The default Java representation of this would be:

public MyClass {
  public MyInterface { }
}

In order to prevent this being bound, our Kotlin fixups instead change it to

private MyClass {
  private MyInterface { }
}

However there is a bug preventing the internal interface from being marked private, because we are setting the visibility on the parent type's InnerClassAccessFlags. When we output the XML we do not check that, we instead look at the flags on the nested type's .class file.

This commit fixes this by finding the appropriate inner class .class file and updating the access flags there (recursively).

In our api.xml, types are flattened. Without this, generator will skip importing the parent type but will import the nested type(s). When it attempts to create the nested model, it cannot find the parent type, resulting in a message like:

warning BG8604: top ancestor MyClass not found for nested type MyClass.MyInterface

[jonpryor]

I wonder if classes should become a KeyedCollection<string, ClassFile>? I'm just worried that if classes gets "big", .FirstOrDefault() may become a time sink.

[jpobst]

Potentially, though this should be a rarely used code path.

[jonpryor]

Shouldn't this .Where() cause all of kf.InnerClasses to be included? How could kf.InnerClasses contain a type for which the inner type's c.OuterClass doesn't match the containing type?

Wouldn't this more easily & efficiently be expressed as:

foreach (var inner_class in kf.InnerClasses) {
}

[jonpryor]

…or does kf.InnerClasses contain "grand-children" as well? For example, in the case of HidePublicInterfaceInInternalClass, will InternalClassWithNestedInterface.class specify InternalClassWithNestedInterface$NestedInterface$DoubleNestedInterface.class as an inner class, even though it's an inner class of InternalClassWithNestedInterface$NestedInterface.class?

[jpobst]

For some reason the InnerClasses collection for an inner class contains itself. Without this check it infinitely recurses into itself.

That is, the InnerClasses for InternalClassWithNestedInterface$NestedInterface contains InternalClassWithNestedInterface$NestedInterface.