Make workload manifest layout own stale outputs

Part of #48070. Give downloaded and built-in workload manifest layout explicit output inventories and stale-output cleanup, including localized content, obsolete feature bands, and obsolete manifest versions. Include baseline workload-set output only when that disabled-by-default feature is enabled.

**Depends on:** #55867.

Start by reading the dependency in #55867 and locating the downloaded and built-in workload manifest layout entry points. Verify how localized content, obsolete feature bands, obsolete manifest versions, and the disabled-by-default baseline workload-set feature are represented. Done means each layout has explicit output inventories and removes stale outputs under the stated feature conditions.

Written by the indexing model from the issue text.