Provide a full Nuxeo Kubernetes deployment sample, using Helm charts

Currently, the only example of a full Nuxeo K8s deployment is through the Platform CI preview. See the Hemlfile section in the Nuxeo Helm chart's README.

It is not trivial to deploy Nuxeo in K8s from this piece of code, which is bound to the CI:

• multiple Helmfile environments: preview, unit tests (no Nuxeo, external services only), etc.
• references to environment variables available in the Jenkins pipeline, such as BRANCH_NAME
• references to the CI K8s cluster through the tolerations and nodeSelector fields
• etc.

Let's provide a simple example of a full Nuxeo deployment, including MongoDB, Elasticsearch and Kafka, usable out of the box and with a minimal configurability.