Deduplicate stored CRDs

[fabriziosestito]

The Image, SBOM, and VulnerabilityReport resources can be deduplicated in storage since they all reference the same image by its sha256 hash.
The sha256 will serve as the primary key for each stored object.
A separate table will also store the name, namespace, and the other resource's metadata—such as registry, repository, image name, and tag labels —linked to the sha256 hash with a foreign key.
When querying by name and namespace, we can retrieve the deduplicated object using the sha256 and substitute the metadata with that of the selected resource.