[APM] Generate Service metrics with synthrace

[kpatticha]

Summary

closes #141024

The datastream is saved as metrics-apm.service-default and can be filtered with metricset.name: service

related to apm-server work

• Service Metrics Aggregator apm-server#8607
• Add _doc_count to Service metrics apm-server#9143

Document generated with synthrace

{
"took": 0,
"timed_out": false,
"_shards": {
  "total": 1,
  "successful": 1,
  "skipped": 0,
  "failed": 0
},
"hits": {
  "total": {
    "value": 109,
    "relation": "eq"
  },
  "max_score": 1,
  "hits": [
    {
      "_index": ".ds-metrics-apm.service-default-2022.09.26-000001",
      "_id": "C_4n-XFHbbdO6p13AAABg3jySm0",
      "_score": 1,
      "_source": {
        "_doc_count": 772,
        "@timestamp": "2022-09-26T08:38:08.237Z",
        "metricset": {
          "name": "service"
        },
        "processor": {
          "event": "metric"
        },
        "service": {
          "name": "web-go-0",
          "environment": "Synthtrace: low_throughput",
          "node": {}
        },
        "transaction": {
          "duration": {
            "summary": {
              "min": 0,
              "max": 3768887.2570648515,
              "sum": 170142852.20549336,
              "value_count": 772
            }
          },
          "failure_count": 116,
          "success_count": 598
        },
        "observer": {
          "type": "synthtrace",
          "version": "8.5.0",
          "version_major": 8
        },
        "ecs": {
          "version": "1.4"
        }
      }
    }
  ]
}
}

Try the changes locally

1. simply run synthrace
   node scripts/synthtrace packages/kbn-apm-synthtrace/src/scenarios/low_throughput.ts --username elastic --local
2. check the datastream metrics-apm.service-default

[kpatticha]

@elasticmachine merge upstream

[kibana-ci]

💚 Build Succeeded

• Buildkite Build
• Commit: b9d1e1b

Metrics [docs]

✅ unchanged

History

• 💔 Build #75530 failed b460c80
• 💔 Build #75521 failed abd85dd0827cc93f970c4f877203fb152b7303b3

To update your PR or re-run it, just comment with:
@elasticmachine merge upstream

[Mpdreamz]

LGTM! thank you for re-aligning this with the server's implementation