<!-- Add the related story/sub-task/bug number, like Resolves#123, or
remove if NA -->
**Related issue:** Resolves#41664
Switching `kernel_host_counts` to the established swap pattern. Reduce
load on the DB writer by moving the large read to the DB reader.
Do `CleanupSoftwareTitles` in batches. With a single large
select/delete, it took > 16 minutes. In batches, it took ~1.5 minutes in
loadtest with 100K hosts.
# Checklist for submitter
If some of the following don't apply, delete the relevant line.
- [x] Changes file added for user-visible changes in `changes/`,
`orbit/changes/` or `ee/fleetd-chrome/changes`.
## Testing
- [x] QA'd all new/changed functionality manually
For unreleased bug fixes in a release candidate, one of:
- [x] Alerted the release DRI if additional load testing is needed
<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->
## Summary by CodeRabbit
* **Performance Improvements**
* Added indexing and a batched swap/insert flow to speed up
vulnerability-related queries and lower maintenance contention.
* Batched cleanup of orphaned records to reduce long-running delete
operations.
* **Reliability**
* Migration removes a legacy constraint to simplify data maintenance and
avoid migration failures.
* Scheduled vulnerability refresh now runs more atomically to reduce
disruption.
* **Tests**
* Updated assertion logic to improve test clarity for host-count
verification.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->
Victor Lyuboslavsky
02e8d474e2