[APM] Migrate `/test/apm_api_integration/tests/service_nodes` to be deployment-agnostic API tests

| API | ESS | Serverless | Test files |
|-----------------------------------|-----|-----|-------------------|
| `GET /internal/apm/services/{serviceName}/metrics/nodes` | ✅ | ❌ | **ESS**: `./test/apm_api_integration/tests/service_nodes/get_service_nodes.spec.ts` |