[Feat] add time-windowed endpoint metrics for load balancing

[tao12345666333]

FILL IN THE PR DESCRIPTION HERE

FIX #227

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👥 vLLM Semantic Team Notification

The following members have been identified for the changed files in this PR and have been automatically assigned:

📁 src

Owners: @rootfs, @Xunzhuo, @wangchen615
Files changed:

• src/semantic-router/cmd/main.go
• src/semantic-router/pkg/config/config.go
• src/semantic-router/pkg/extproc/processor_req_body.go
• src/semantic-router/pkg/extproc/processor_req_header.go
• src/semantic-router/pkg/extproc/processor_res_body.go
• src/semantic-router/pkg/observability/metrics/windowed_metrics.go
• src/semantic-router/pkg/observability/metrics/windowed_metrics_test.go

📁 website

Owners: @Xunzhuo, @rootfs, @yuluo-yx
Files changed:

• website/docs/tutorials/observability/metrics.md

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🎉 Thanks for your contributions!

This comment was automatically generated based on the OWNER files in the repository.

[Xunzhuo]

We will deprecate and not use vllm_endpoints in k8s, instead, we care about what model to use, not which ip to use. So my quesion is, can we move the scoring logics up to model level not endpoint level ?

[tao12345666333]

Sure. Let me update it.

[rootfs]

@tao12345666333 do you have an output of the metrics from a running router we can see?