static <T> Optional<Equivalence.Wrapper<T>> wrapOptionalInEquivalence(
      Equivalence<T> equivalence, Optional<T> optional) {
    return optional.map(equivalence::wrap);
  }
Wraps an {@link Optional} of a type in an {@code Optional} of a {@link Equivalence.Wrapper} for
that type.
factory/src/main/java/com/google/auto/factory/processor/Mirrors.java