Add `collection.effective_ancestors` to model search results (#41746)

* Add `collection.effective_ancestors` to search

Fixes #41909

The ultimate goal here is to be able to display a UI that showed the entire (effective) path to each collection.

This was a bit more painful than I'd hoped. The primary issue is that we
tied two things together:

- scoring results

- "serializing" results (really, partially serializing results, because
we do more work to shape the data later)

Why is this a problem? The `top-scorers` function took a transducer and
returned the *serialized* top scorers. Later, when we need to operate
on *all* the top results (in this case, to collect all the collection
IDs and names that we know of), we're looking at the serialized results.

In our case, we needed some data (collection location) that wasn't
included after serialization. We could add it, of course, but it's
frustrating to need to change the API of what data is *returned* from
the endpoint for purely internal purposes (changing the data available
during *processing*).

I ended up pulling serialization out of the scoring function. At some
point down the road, we should go ahead and move the `serialize`
function out of the `search.scoring` namespace entirely - there's really
no reason for it to belong there as far as I can tell.