Image refs in containerfiles/dockerfiles should consistently use digests.

Joseph said in https://gitlab.cee.redhat.com/rhidp/rhdh/-/merge_requests/327/diffs#note_17924191

The thing is... 'rhdh' repo doesn't use digest, but 'rhdh-operator' does. That's why we use '--sha' for 'rhdh-operator'. Armel offered that they can omit the digest on renovate - need to open a JIRA issue if we go this path.
e.g. https://github.com/redhat-developer/rhdh/commit/d993c704abd01d2f88f0626c26452c6cf597dba4
vs.
https://github.com/redhat-developer/rhdh-operator/commit/5e7d564b38285e96d3bec37a0d07d56b3ae77130

So the DoD here is:

• use digests in Dockerfiles in rhdh repo, like we already do for operator
• update renovate config in rhdh repo to use digests, like we already do for operator
• update the updateBaseImages.sh script so that it too uses pinned sha digests as well (the --sha flag should be on by default)