codeintel: use COUNT OVER() window function for getting uploads/indexes total count

Created by: Strum355

May or may not close #34915 (closed) by implementing the approach from the linked stackoverflow issue. Performance improvements weren't stable (sometimes faster, sometimes on-par), so I want to observe this in production for a while to see how the average case does, given we're only having to make one query here instead of two, the overhead saved may work in its favour.

Test plan

Covered by existing tests and dashboards