CifCollectUtils methods should return the collection

From discussion at !281 (comment 627855):

I'm thinking, can we make the methods also return the list. I know it is an argument and the caller already has it. But now we typically use it as follows:

        List<Event> events = list();
        collectEvents(spec, events);

If it would also return the list, we could do:

        List<Event> events = collectEvents(spec, list());

This would be backward compatible, I think.

To still allow passing any type of collection, it would be something like this then:

    public static <T extends Collection<Event>> T collectEvents(ComplexComponent comp, T events) {
        ...
    }

I'm wondering, would it be useful to also have:

    public static List<Event> collectEvents(ComplexComponent comp) {
        return collectEvents(spec, list());
    }

It would allow using it like:

        List<Event> events = collectEvents(spec);

Without having to provide a collection. Although the added benefit is not super great.

Yup, I was thinking that too, but as a separate step.

I like your T extends Collection<Event>. It's a nice solution, didn't think of that.

This issue is to address that follow-up to #330 (closed).