[Router][Bugfix] make healthcheck timeout customizable

[max-wittig]

30 second timeout per model is enough for most people but somebody might use a very big model or use slow machines so it should also work for this use case.

Customizing the health check interval will be done in another MR.

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Summary of Changes

Hello @max-wittig, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request introduces a new configuration option for the vllm_router to allow users to customize the timeout for static backend health checks. This enhancement addresses scenarios where the default 30-second timeout might be insufficient for larger models or slower infrastructure, improving the router's adaptability and robustness.

Highlights

• Configurable Health Check Timeout: The static backend health check timeout, previously hardcoded to 30 seconds, is now customizable. This allows users to adjust the timeout for large models or slower environments, preventing premature health check failures.
• New CLI Argument: A new command-line argument, --static-backend-health-checks-timeout, has been introduced in src/vllm_router/parsers/parser.py. It accepts an integer value for the timeout in seconds and defaults to 30.
• Service Discovery Integration: The ServiceDiscovery class in src/vllm_router/service_discovery.py has been updated to accept and store the new timeout value, which is then passed to the is_model_healthy utility function during health checks.
• Utility Function Update: The is_model_healthy function in src/vllm_router/utils.py now accepts a timeout parameter, making the underlying HTTP request timeout configurable.

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Code Review

The pull request introduces a customizable timeout for health checks, which is a valuable enhancement for users with large models or slower machines. The changes include adding a new argument to the parser, passing the timeout value through the service discovery, and using it in the health check function. The code is well-structured and the changes are focused on the intended functionality.