[elasticapm] Remove service_summary metric for metrics-only services

[rogercoll]

Kibana showing pods as APM services due the signaltometrics connector creating metrics for any service (signal with service.name attribute):

It can be replicated by deploying the OTel operator with: https://github.com/elastic/elastic-agent/blob/8.17/deploy/helm/edot-collector/kube-stack/managed_otlp/values.yaml (change image reference to 8.17.2)

[rogercoll]

An alternative would be to not use the signaltometrics connector for metrics/logs-only services as configured in the operator's values configuration: https://github.com/elastic/elastic-agent/blob/8.x/deploy/helm/edot-collector/kube-stack/values.yaml#L892

For filelog receiver logs the agent.name value was set to unknown if not provided (temporally workaround): https://github.com/elastic/elastic-agent/blob/8.x/deploy/helm/edot-collector/kube-stack/values.yaml#L575

[lahsivjar]

Talked with @felixbarny and we decided to remove the elasticapm connector from the metrics pipeline. This would mean that when/if we add support for metrics in the elasticapm connector we would need to update the pipelines again.

I will work on a PR for this.

[lahsivjar]

MOTel

The changes for MOTel are done via https://github.com/elastic/hosted-otel-collector/pull/495

EDOT

The changes for adding elasticapm connector are released for the 9.0 branch with elastic/elastic-agent#7172 PR. The PR for main branch is still blocked by the corresponding version up PR for OTel components.