@Override
    public MatcherDef extendsWildcard(Type.Wildcard.Extends wildcard) {
      throw new AssertionError();
    }
Criteria templates are always generated as top-level class (separate file).
Construct criteria name from {@linkplain TypeMirror}

@return fully qualified criteria (template) class name
value-processor/src/org/immutables/value/processor/meta/CriteriaModel.java