[TPU] Add example for profiling TPU inference

[mgoin]

Provides an example for simple prefill or decode profiling on TPUs. This is a starting point equivalent to text-only inference using benchmark_latency.py, where all the user can specify is batch size, input length, and output length.

Future work should expand this example to cover realistic data and multimodal inference.

Example screenshot of a profile in tensorboard (tensorboard --logdir profiles/ --port 6006):

[github-actions]

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