[AutoOps] Display Actual API Error Message from Cloud Connected

[pickypg]

When AutoOps receives an error from the Cloud Connected API, it hides the error unintentionally.

failed to register for Cloud Connected Mode: failed to fetch data: HTTP error 400 Bad Request

However, the Cloud Connected API returns a structured error object and we should display any error presented to the end user, like:

{
  "errors": [
    {
      "code": "clusters.create_cluster.license_already_in_use",
      "message":"license is already in use in a different organization"
    }
  ]
}

Relevant code is here:

beats/x-pack/metricbeat/module/autoops_es/metricset/register.go

Lines 145 to 153 in f6a858e

	data, err := utils.HandleHTTPResponse[cloudConnectedResource](http.DefaultClient.Do(req)) //nolint:bodyclose // the handler closes the body
	if err == nil {
	utils.SetResourceID(data.ID)
	logger.Infof("Registered cluster %s for Cloud Connected Mode: %s", clusterInfo.ClusterID, data.ID)
	return nil
	}
	return fmt.Errorf("failed to register for Cloud Connected Mode: %w", err)