Contains two fixes for the archive purging system:
1) For purging invalidated archives, includes an extra group by in the GROUP_CONCAT query used to find invalidated archives that can be purged. By grouping by
name too, we get less idarchives per row, which means the GROUP_CONCAT limit should not be hit.
2) Fixes a regression where the purgeOutdatedArchives task was skipped because it could no longer tell if it was executed during the core:archive command (since it does not use CliMulti anymore). Includes two new (light) tests for this use case.
Refs #7181 (should fix it, but will need confirmation)