Modify metrics service endpoint

[lambert0312]

Motivation

When using sglang to deploy LLM in the K8s environment, use the --enable-metrics parameter to open the /metrics endpoint. If the api-key is configured, it will cause problems in obtaining monitoring data.

Modifications

Similar to /health, exclude the /metrics endpoint from verifying the api-key

Checklist

• Format your code according to the Code Formatting with Pre-Commit.
• Add unit tests as outlined in the Running Unit Tests.
• Update documentation / docstrings / example tutorials as needed, according to Writing Documentation.
• Provide throughput / latency benchmark results and accuracy evaluation results as needed, according to Benchmark and Profiling and Accuracy Results.
• For reviewers: If you haven't made any contributions to this PR and are only assisting with merging the main branch, please remove yourself as a co-author when merging the PR.

[Swipe4057]

Oh, this is one of the reasons why it was difficult to set up Prometheus+Grafana metrics collection. The documentation doesn't mention anywhere that a password is required for the /metrics endpoint. I had to specify the password manually. I'm writing down all the errors I encountered here: #2677 (comment). If you use vLLM, then by default, no password is required for metrics collection, as suggested in this PR.

[lambert0312]

Oh, this is one of the reasons why it was difficult to set up Prometheus+Grafana metrics collection. The documentation doesn't mention anywhere that a password is required for the /metrics endpoint. I had to specify the password manually. I'm writing down all the errors I encountered here: #2677 (comment). If you use vLLM, then by default, no password is required for metrics collection, as suggested in this PR.

Yes, this is the reason why I mentioned this PR, otherwise it will make collecting monitoring data more complicated.

[lambert0312]

Anything missing? @zhyncs