## Summary

Closes elastic/ingest-dev#1261

Merged: [elasticsearch
change](elastic/elasticsearch#91701) to give
kibana_system the missing privilege to read logs-elastic_agent* indices.

## Top 3 most common errors in the Elastic Agent logs

Added most common elastic-agent and fleet-server logs to telemetry.

Using a query of message field using sampler and categorize text
aggregation. This is a workaround as we can't directly do aggregation on
`message` field.
```
GET logs-elastic_agent*/_search
{
    "size": 0,
    "query": {
        "bool": {
            "must": [
                {
                    "term": {
                        "log.level": "error"
                    }
                },
                {
                    "range": {
                        "@timestamp": {
                            "gte": "now-1h"
                        }
                    }
                }
            ]
        }
    },
    "aggregations": {
        "message_sample": {
            "sampler": {
                "shard_size": 200
            },
            "aggs": {
                "categories": {
                    "categorize_text": {
                        "field": "message",
                        "size": 10
                    }
                }
            }
        }
    }
}
```

Tested with latest Elasticsearch snapshot, and verified that the logs
are added to telemetry:
```
   {
      "agent_logs_top_errors": [
         "failed to dispatch actions error failed reloading q q q nil nil config failed reloading artifact config for composed snapshot.downloader failed to generate snapshot config failed to detect remote snapshot repo proceeding with configured not an agent uri",
         "fleet-server stderr level info time message No applicable limit for agents using default \\n level info time message No applicable limit for agents using default \\n",
         "stderr panic close of closed channel n ngoroutine running Stop"
      ],
      "fleet_server_logs_top_errors": [
         "Dispatch abort response",
         "error while closing",
         "failed to take ownership"
      ]
   }
```

Did some measurements locally, and the query took a few ms only. I'll
try to check with larger datasets in elastic agent logs too.


### Checklist

- [x] [Unit or functional
tests](https://www.elastic.co/guide/en/kibana/master/development-tests.html)
were updated or added to match the most common scenarios

Co-authored-by: Kibana Machine <42973632+kibanamachine@users.noreply.github.com>

#146507)

## Summary

Backport #146107 to 8.6

Co-authored-by: Kibana Machine <42973632+kibanamachine@users.noreply.github.com>