proxy: support super traits

[tjhu]

Super trait was not supported because it requires type resolution, which we didn't have. Now we have a working type resolution, we should implement the support for super trait.

To support this, the ngc needs to generate the following in the proxy given trait Trait: SuperTrait:

impl SuperTrait for TraitProxy {
  fn method(&self) -> {
    // Proxied called ....
  }
}