Added otlp

[AICrafterZheng]

Description

Enabling comprehensive observability for GraphRAG with OpenTelemetry and Zipkin as the tracing backend, which can then be easily integrated into any product that uses GraphRAG.

Related Issues

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Proposed Changes

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Checklist

• [x] I have tested these changes locally.
• [x] I have reviewed the code changes.
• [x] I have updated the documentation (if necessary).
• [ ] I have added appropriate unit tests (if applicable).

Additional Notes

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