Add image download support in CLI

[George-Aeillo]

In the CLI, while we support using the catalog mirror and catalog copy commands to transfer images from a public registry to a private registry, this assumes that the private registry is accessible from the location where the catalog mirror or catalog copy command is ran. In air-gapped environments, this may not always be the case, so support should be added to downloading and archiving these images on disk, so that the archived file can be transferred to an air-gapped environment.