Add Elasticsearch version check to New Platform

[rudolf]

In the legacy Platform the elasticsearch plugin did a healthcheck that included checking that all Elasticsearch nodes in the cluster match that of Kibana.

In #14163 we decided to abandon the polling health check. Although the reasons for abandoning the health check still stand, we will have to keep polling to do the version check since new Elasticsearch nodes can join an existing cluster after Kibana has started up.

[afharo]

I'm finding this task can only be partially done because the Status plugin has not been migrated to the New Platform yet. I think we'll need to expose another service to the Plugins to report their status (#41983).