[AutoOps] Restructure `error` type

[pickypg]

We should restructure the error object that we ship from the autoops_es module so that the errors can be more easily used.

Specifically, we currently nest a custom error object under whatever metricset resulted in the error and we use ECS-formatted field names within the error object. We should take those fields and put them at the root.

It would be nice to have errors look more like this:

{
  "@timestamp": "2026-02-03T02:31:00.183Z",
  "@metadata": {
    "beat": "metricbeat",
    "type": "_doc",
    "version": "9.4.0"
  },
  "agent": {
    "id": "fe280bcd-e74a-4ee1-ac5a-eeda0553e0cb",
    "name": "my-host",
    "type": "metricbeat",
    "version": "9.4.0",
    "ephemeral_id": "134a30da-09a5-49dc-bef6-071a6cf35f39"
  },
  "ecs": {
    "version": "8.0.0"
  },
  "url": {
    "path": "/",
    "query": ""
  },
  "service": {
    "address": "http://mycluster:1234",
    "type": "autoops_es"
  },
  "autoops_es": {
    "transaction_id": "019c2156-c35d-73bf-8d0d-b127bcbf344a",
    "cluster": {
      "id": "",
      "name": "",
      "version": ""
    }
  },
  "event": {
    "kind": "metric",
    "dataset": "autoops_es.node_stats",
    "module": "autoops_es",
    "duration": 6192875,
    "type": "error"
  },
  "http": {
    "request": {
      "method": "GET"
    },
    "response": {
      "status_code": 0
    }
  },
  "metricset": {
    "name": "node_stats",
    "period": 10000
  },
  "error": {
    "code": "HTTP_0",
    "message": "failed to send request: error making http request: Get \"http://mycluster:1234/\": lookup es-customer: no such host"
  },
  "orchestrator": {
    "resource": {
      "id": "abc123"
    }
  },
  "host": {
    "name": "my-host"
  }
}

[consulthys]

Good call @pickypg
Does this mean that the error metric set is gone and we're adding the error to the effective metric set documents? (i.e. there's no error.metricset field anymore)

Let's also please make sure to add those fields to the index mapping so they are properly indexed:

• error.message: keyword
• error.description: keyword
• http.response.status_code: short