Enrich nuxeo-docker-cfg with all authentications

We want to enrich the secret created during NXBT-3255 and named nexus-docker-cfg with all authentications present in the jenkins-docker-cfg.

As the secret won't have nexus auth only, we could rename it to kubernetes-docker-cfg.

This will allow us to copy/replicate only one secret when we need to access our internal docker registry and another private registry (as packages) in the same helm chart.