Add tests to make sure that `Base.project_names`, `Base.manifest_names`, `Base.preferences_names`, and `Artifacts.artifact_names` always have the same length (#40618)
* Add tests to make sure that `Base.project_names`, `Base.manifest_names`, `Base.preferences_names`, and `Artifacts.artifact_names` always have the same length
* Add a comment explaining why we have these tests