Data Prepper 2.16: Improved end-to-end metrics

OpenSearch Data Prepper 2.16 has been released, introducing a new pull-based Prometheus source and direct ingestion support for the OpenSearch Time-Series Database (TSDB). The update also features experimental support for pull-based ingestion via Kafka and significant enhancements to both OpenSearch and OTLP sinks, including expanded support for OpenTelemetry logs.