Extend StorageObjectUpload() to allow setting custom metadata on the
uploaded object.
Modify worker's osbuild job implementation and GCP CLI upload tool to
set the chosen image name as a custom metadata on the uploaded object.
This will make it possible to connect Storage objects to specific
images.
Add News entry about image name being added as metadata to uploaded GCP
Storage object as part of worker job.
Signed-off-by: Tomas Hozza <thozza@redhat.com>