Kubernetes attributes promoted to release candidate in OTel Semantic Conventions

Kubernetes attributes within the OpenTelemetry (OTel) framework have reached “release candidate” status, meaning they are nearing a stable, finalized schema. This milestone was achieved by focusing on stabilizing attributes used by key OTel Collector components like `k8sattributes` and `resourcedetection`, aligning with broader Collector stability goals. Users can now test the new schema via feature gates and provide feedback before the attributes are officially declared stable.