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

• [x] 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.