keep the "old" scalar queries behaviour with offset or limit

[i-just]

Description

The performance changes from 0ff4796 are causing slightly different behaviour when running scalar element queries.

The first reported case points out that before 4.9, in the EntryQuery::EVENT_BEFORE_PREPARE, for the scalar queries, the $event->sender->orderBy used to return null, but now it’s returning an empty string.

The second reported case is a combination of search, limit, and orderBy('score') params. Prior to 4.9, running count() on a query that contained all three would still return the total count, but now, it respects the passed-in limit. That’s because, in this case, the prepared subquery contains the IDs of the searched elements and the query that got those IDs respected the set limit. (Using the offset param would result in the same non-total count now.)

I raised a PR to go back to the “old” approach when the query contains offset or limit.

I’m raising this as a draft in case we want to discuss this further in the CMS meeting.

Related issues

#15001

[brandonkelly]

Resolved via dc36833 while still maintaining the performance improvement.