ConstraintStreams: Add collector for toList()

public final class ConstraintCollectors {

    public static <A> UniConstraintCollector<A, ?, List<A>> toList() {
        return new DefaultUniConstraintCollector<>(
                () -> new ArrayList<A>(),
                (resultContainer, a) -> {
                    resultContainer.add(a);
                    return (() -> resultContainer.remove(a));
                },
                resultContainer -> resultContainer);
    }

 public static <A, Property_> UniConstraintCollector<A, ?, List<Property_>> toList(Function<A,Property_> groupValueMapping)