wrap-java: Generated @JavaInterfaces must have JavaObject base functions

[ktoso]

The way we're generating Swift types for interfaces is problematic:

@JavaInterface("java.lang.reflect.TypeVariable", extends: Type.self)
public struct TypeVariable<D: AnyJavaObject> {
  @JavaMethod
  public func getGenericDeclaration() -> GenericDeclaration!
  
  @JavaMethod
  public func getAnnotatedBounds() -> [AnnotatedType?]

while we know we can call hashCode, equals and toString on those types... Lack of those on extracted types means we can't make ALL java types Hashable, which makes interfaces hard to work with -- and since a lot of java is interface based, that's not ideal.

It also makes our description->toString problematic.

[ktoso]

We could perhaps make them final classes and inherit from JavaObject