[Reporting] Background poller runs regardless of ES health

[elasticmachine]

Original comment by @pickypg:

While debugging an unrelated issue last night, I noticed that regardless of the connection's health, Reporting will constantly fire its background poller.

It seems reasonable that it should be something more along the lines of:

let poller = null;

server.plugins.elasticsearch.status.on('green', () => {
  if (!poller) {
    poller = setInterval(trigger, config.get('xpack.reporting.poll_interval'));
  }
});

server.plugins.monitoring.status.on('red', () => {
  clearInterval(poller);
  poller = null;
});

[elasticmachine]

Original comment by @kobelb:

@pickypg this situation should improve by the backoffs introduced by LINK REDACTED but I could see the desire to suspend polling based on the Elasticsearch's status as well.

[elasticmachine]

Pinging @elastic/kibana-reporting-services (Team:Reporting Services)

[tsullivan]

The proposed solution wouldn't work in Kibana New Platform. I am not sure that the New Platform will "automatically" solve this though. This question is one to track on the Reporting New Platform Migration issue: #53898