PackageMetadata synchronization needs to verify license

Summary

Package Metadata synchronization is an ultimate feature used by license_scanning.

But because the sync worker does not check if the feature is available synchronization will run on instances that are not ultimate licensed.

Possible fixes

According to the license model self-managed subscriptions are installed at an instance level and GitLab SaaS is a special self-managed instance that is Ultimate. So it should be enough to check whether the license_scanning feature is available.

Implementation plan

• update PackageMetadata::Syncworker to check whether license_scanning is available before running