Fix some issues with benchmark data output

[huydhn]

This is a follow-up of #13068 to fix:

• Handle the inf qps config. The JSON parser used by the database doesn't like this value. So, I add a custom InfEncoder to convert this to an inf string.
• Passing the parameter --tensor-parallel-size to benchmark_serving.py script so that it can be stored in JSON and picked up by the dashboard. I'll use --metadata to get this instead per @ywang96 comment
• Handle missing .commands because the new .pytorch.json is also a JSON file.

cc @ywang96 @simon-mo

Just FYI, here is a preview of the new dashboard.

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[ywang96]

If you just need a way to pass tp as an argument to this script, we already have --metadata

[huydhn]

Ah got it, --metadata is indeed more appropriate for this as I just need to get tp parameter to show on the dashboard. It's probably a good idea to save other server parameters too just in case.

[ywang96]

LGTM! Thanks for the fix and addressing my comment!