_InterfaceMethod does not expose annotations

[postelrich]

The _InterfaceMethod does not expose the annotations described in the capnp schema. Particularly:

interface MyInterface $baz(7) {
  myMethod @0 (myParam :Text $baz(9)) -> () $baz(8);
}

which in this case would be $baz(8) the annotation on the method. Only param_type and result_type are exposed.