Saved Search inconsistencies around unpublished datasets

[scolapasta]

Found by @kcondon during testing of #7447

Performed a search, got X results.
Added as a saved search to a brand new DV, only showed Y results (Y bring less than X).

Looking at it further, the missing results were for harvested datasets (should we include these?).

But the other missing where (some) unpublished datasets. Why only some? Well, the going hypothesis (from looking at both code and results) is that:
• Unpublished datasets cannot be directly linked
• however, when unpublished datasets in a linked, published dataverse are indexed, they get indexed as links.

This seems inconsistent and we should establish consistent rules.