Bug 1800670 - We were able to publish an image bundle to redhat-operators containing references to unpublished images

Tracking JIRA for https://bugzilla.redhat.com/show_bug.cgi?id=1800670

Description of problem:
I'm not 100% sure I should open this here on on the errata tools; feel free to move this to the right component.

The image bundle is now the de facto mechanism to publish OLM (operators) based applications.
Currently the image bundle is just an image which content (the bundle) is almost completely opaque to the errata tool while the user will be instead going to consume the content of the bundle.

In our case, see bug https://bugzilla.redhat.com/1797804 , we were able to publish to redhat-operators catalog a bundle containing references to unreleased, and so unavailable, images and this broken `oc adm catalog build` mirroring mechanism.

Version-Release number of selected component (if applicable):

How reproducible:
100%

Steps to Reproduce:
1. create a bundle image with link to unexisting images
2. attach it to an errata, move it to staging and then ship to prod
3.

Actual results:
The broken bundle is consumable from redhat-operators but the images are not there

Expected results:
Something at errata level should inspect the bundle and/or something at appregistry level should reject bundles with unexisting images