Drop ci_runners_archived and ci_runner_machines_archived

After a few milestones of #504963 (closed) being closed, and we're confident that we won't need the archived tables, we should drop ci_runners_archived and ci_runner_machines_archived. We should then rename the indices of the new replacement partitioned tables to take over the old names. They currently have slightly cryptic names because of the character limit due to the longer partitioned table names. For example:

TODO

• Tidy up loose_foreign_keys_deleted_records records which are pointing to *_archived tables, so they point to the new tables (Slack)