Optimizing MySQL master DB based on customer feedback

[getvictor]

#18838

1. During software ingestion, switched to updating last_updated_at as a batch for 1 host.
2. Removed DELETE FROM software statement that ran for every host update (where software was deleted). This is only done now during the vulnerability job.

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. See Changes files for more information.
• [x] Added/updated tests
• [x] Manual QA for all new/changed functionality