Detect auto-deploy tags while waiting for images

Closes: #2054 (closed)

Decisions I took

1. sync-images is not ran on auto-deploy tags. This means the images will never reach com. So waiting for them is useless right now. Let's just check if the images exist in dev registry (i.e, whether CNG did its job). This process will anyway have to be rethought when we do #1442 (closed) and #1412 (closed)
2. Let go of "While building on git tags, the docker image tags must match the git tag" because auto-deploy tag format is invalid for a docker image. I just converted it to a slug and called it a day. This works, because the image is anyway tagged using its slug