Add args for mTLS support

[declark1]

This PR exposes additional uvicorn TLS args ssl_ca_certs, ssl_cert_reqs to enable mTLS support.

[ywang96]

@simon-mo Hmmm...this PR probably shouldn't be merged in the first place since it's making changes to vllm/entrypoints/api_server.py. I wonder if we should make a workflow to automatically warn user if the changes are being made to that file.

@declark1 Could you please make a PR to add this to vllm/entrypoints/openai/api_server.py as well?

[declark1]

Thanks for pointing this out @ywang96, my apologies for missing that. I have opened a new PR to fix this.

[simon-mo]

I merged this because benchmarking over mTLS is a valid use case.