Change the auto-deploy tag depending on builder
- The auto-deploy tag does not make sense if we carry the current tag over into other builders.
- The omnibus sha is specific to omnibus, but not helm or CNG builds
- This updates our readme with the defined tag we've determined is good enough to iterate and unique enough to determine what is to be deployed into our environments
Addresses: gitlab-com/gl-infra/delivery#693 (closed)