Update the return type of getMyData use case

[ekraffmiller]

The return type of getMyDataCollectionItems is CollectionItemSubset, which is shared with getCollectionItems. This works by formatting the PublicationStatus results as facets, which was meant to be extensible, but is awkward to use in the frontend code and is a different format from the data returned from the dataverse API.

So this issue it to update the return type so it returns a list of PublicationStatus counts, rather than facets.