[Feature Request]: OpenTelemetry Support

### What would you like to happen?

This is more a question than a feature request.

I was wondering... Why I don't see any OpenTelemetry related issue on Apache Beam? Is it because the runners already provide observability about their jobs?

I'm more interested in the Python side for now, but if there's no reason, would it make sense to create a `opentelemetry-instrumentation-apache-beam` package?

### Issue Priority

Priority: 3 (nice-to-have improvement)

### Issue Components

- [X] Component: Python SDK
- [ ] Component: Java SDK
- [ ] Component: Go SDK
- [ ] Component: Typescript SDK
- [ ] Component: IO connector
- [ ] Component: Beam YAML
- [ ] Component: Beam examples
- [ ] Component: Beam playground
- [ ] Component: Beam katas
- [ ] Component: Website
- [ ] Component: Infrastructure
- [ ] Component: Spark Runner
- [ ] Component: Flink Runner
- [ ] Component: Samza Runner
- [ ] Component: Twister2 Runner
- [ ] Component: Hazelcast Jet Runner
- [ ] Component: Google Cloud Dataflow Runner

Start with the Python SDK and existing runner observability described in the issue, then determine whether Apache Beam needs native OpenTelemetry support or a separate instrumentation package. Done means reaching a concrete scope and implementation decision for Python, including whether an opentelemetry-instrumentation-apache-beam package is appropriate.

Written by the indexing model from the issue text.