Allow automatic Elasticsearch nodes discovery

[barkbay]

This PR allows automatic discovery of Elasticsearch nodes by clients which support "sniffing" mode.

More precisely it:

• Sets http.publish_host to the Pod hostname (in the form $(podname).$(governing service domain).$(namespace).svc). Note that it is different from network.publish_host, therefore I think we should not hit TestMutationHTTPToHTTPS is flaky  #3723 again.
• Adds the DNS wildcards *.$(governing service domain).$(namespace).svc in the HTTP self signed certificate, for example:

        X509v3 extensions:
            X509v3 Key Usage: critical
                Digital Signature, Key Encipherment
            X509v3 Extended Key Usage:
                TLS Web Server Authentication, TLS Web Client Authentication
            X509v3 Subject Alternative Name:
                DNS:elasticsearch-sample-es-http.default.es.local,
                DNS:elasticsearch-sample-es-http,
                DNS:elasticsearch-sample-es-http.default.svc,
                DNS:elasticsearch-sample-es-http.default,
                DNS:*.elasticsearch-sample-es-default.default.svc

Autodiscovery mostly makes sense if the client has an interface in the Kubernetes network. Therefore DNS wildcards are added automatically in the SANs only in the self signed certificate.

IPs are ephemeral in a Kubernetes cluster, I think it is fair to assume that DNS issues should be handled by the client. During my tests with the Node.js client it has always been able to gently reconnect to the cluster while I was randomly deleting the Elasticsearch Pods.

A sample based on the official ones is available here if you want to test that feature.

Fixes #3182

[barkbay]

jenkins test this please

[sebgl]

LGTM, just one naming suggestion.