[feat][router][tracing]: implement request tracing using OpenTelemetry with trace context propagation (HTTP)

[sufeng-buaa]

Motivation

Create OpenTelemetry spans to trace requests execution and enable aggregation with the engine's traces, enhancing observability.

Modifications

1. Add an OpenTelemetry layer to the tracing crate, enabling tracing data from tracing::span!() and tracing::event!() macros to be exported to the OTel Collector.
2. Add a filter to prevent existing tracing::info!(), tracing::debug!(), and tracing::error!() logs in the project from being exported to the OTel Collector.
3. Implement trace context propagation for the HTTP router.

TODO

1. Trace context propagation for the gRPC router.
2. The gRPC entrypoint in the engine has not yet been adapted for request tracing either.

Checklist

• Format your code according to the Format code with pre-commit.
• Add unit tests according to the Run and add unit tests.
• Update documentation according to Write documentations.
• Provide accuracy and speed benchmark results according to Test the accuracy and Benchmark the speed.
• Follow the SGLang code style guidance.
• Work with maintainers to merge your PR. See the PR Merge Process

[gemini-code-assist]

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[stmatengss]

/tag-and-rerun-ci

[slin1237]

can you rebase to latest

[sufeng-buaa]

can you rebase to latest

done👌