Add livez and readyz endpoints

[petrosbaltzis]

Update api_server to include livez and readyz endpoints. These endpoints are helpful for Kubernetes deployment: https://kubernetes.io/docs/reference/using-api/health-checks/

[zhuohan123]

Thank you for your contribution! Our goal of api_server.py is to provide a minimal example of an API server. Adding these endpoints will add unnecessary complexity for api_server.py. For your use case, you can make a copy of api_server.py and modify the server for your needs accordingly.

[allenhaozi]

Thank you for your contribution! Our goal of api_server.py is to provide a minimal example of an API server. Adding these endpoints will add unnecessary complexity for api_server.py. For your use case, you can make a copy of api_server.py and modify the server for your needs accordingly.

@zhuohan123 I strongly agree to keep api_server.py as simple as possible

However, almost all private cloud platforms are deployed by kubernetes. If a healthy check function can be provided, most users will not need to maintain an api_server.py independently, which will bring great convenience to vllm users. Because maintaining the branch alone is a very expensive thing to do

If possible, I hope you can reconsider this function, thank you

cc @avnishn