Add job to clean up hawkbit artifacts

The apertis-image-recipes CI/CD pipeline is adding artifacts to hawkBit. This rapidly grows the artifact pool, which are also stored on images.apertis.org. It is not desirable for this to grow indefinitely, so clean out artifacts older than 7 days for now.

This will need adding as a CI scheduled pipeline and the HAWKBIT_USERNAME and HAWKBIT_PASSWORD CI/CD variables set.

Signed-off-by: Martyn Welch martyn.welch@collabora.com