Basic performance logging for Llama python runner

[jackzhxng]

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[pytorch-bot]

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✅ You can merge normally! (1 Unrelated Failure)

As of commit 6974b76 with merge base 01c2f36 ():

FLAKY - The following job failed but was likely due to flakiness present on trunk:

• pull / unittest-buck / linux / linux-job (gh) (matched linux rule in flaky-rules.json)
  Error response from daemon: Get "https://308535385114.dkr.ecr.us-east-1.amazonaws.com/v2/": net/http: request canceled while waiting for connection (Client.Timeout exceeded while awaiting headers)

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[lucylq]

Lgtm! What are you trying to log times for btw?

[jackzhxng]

@lucylq models like Qwen and Phi which we don't have json tokenizer cpp support for yet :'|