Stack monitoring.kibana - 8.0 compatibility

[klacabane]

This ticket tracks the changes required to make the SM kibana section compatible with metricbeat 8.x.

• SM: some kibana queries have outdated assumptions about the stored data structure. It assumes a nested kibana.kibana object but I does not exist anymore (a similar property was deleted ~8months ago from metricbeat which is possibly the cause) fix kibana metricsets property paths #122034
• kibana.stats: extract correct index property beats#29622
• metricbeat: the elasticsearch.cluster.id property should be assigned to RootFields instead of ModuleFields Write to rootfields instead of modulefields beats#29494

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Agent only

• missing cluster_uuid alias to elasticsearch.cluster.id
• missing kibana_stats.timestamp alias to @timestamp
• missing kibana_stats.kibana.uuid alias to service.id
• missing kibana_stats.kibana.status alias to kibana.stats.status

[elasticmachine]

Pinging @elastic/infra-monitoring-ui (Team:Infra Monitoring UI)