PQ storage should be sorted by row ID

When we store PQ data (e.g. in an IVF_PQ index) I do not believe it is sorted by row ID. However, there is no downside to doing so, we just need to sort before we write during the shuffling process.

If we can do that, and guarantee that the PQ data is sorted by row ID, then we can speed up prefiltering. The slowest part of prefiltering currently is not the secondary index search to get the matching row IDs. The slowest part is actually applying that prefilter to the PQ search. This is because we have to sort the PQ data by row ID and then filter it. If the PQ data is already sorted we can skip that step and speed up prefiltering.

Start by tracing the IVF_PQ shuffling process where PQ data is written. Confirm how row IDs are ordered before storage, then ensure the stored PQ data remains sorted by row ID so prefiltering no longer needs to sort it before filtering.