[Frontend] add tok/s speed metric to llm class when using tqdm

[MahmoudAshraf97]

This PR adds a speed metric to the progress bar when using tqdm

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[DamianB-BitFlipper]

This contribution would be much appreciated!

[MahmoudAshraf97]

@mgoin Sorry to bother you, I guess the failures in the CI aren't related to my change

[simon-mo]

This is erroring in CI

https://buildkite.com/vllm/ci/builds/6751#018f529b-4a51-431a-b1d0-0a4daeb8d49f/319-360

35%|███▌      | 7/20 [00:04<00:08,  1.55it/s]--- Logging error ---
Traceback (most recent call last):
  File "/usr/lib/python3.10/logging/__init__.py", line 1100, in emit
    msg = self.format(record)
  File "/usr/lib/python3.10/logging/__init__.py", line 943, in format
    return fmt.format(record)
  File "/usr/local/lib/python3.10/dist-packages/vllm/logger.py", line 24, in format
    msg = logging.Formatter.format(self, record)
  File "/usr/lib/python3.10/logging/__init__.py", line 678, in format
    record.message = record.getMessage()
  File "/usr/lib/python3.10/logging/__init__.py", line 368, in getMessage
    msg = msg % self.args
ValueError: unsupported format character ',' (0x2c) at index 159
Call stack:
  File "/usr/lib/python3.10/runpy.py", line 196, in _run_module_as_main
    return _run_code(code, main_globals, None,
  File "/usr/lib/python3.10/runpy.py", line 86, in _run_code
    exec(code, run_globals)
  File "/usr/local/lib/python3.10/dist-packages/vllm/entrypoints/openai/api_server.py", line 169, in <module>
    uvicorn.run(app,
  File "/usr/local/lib/python3.10/dist-packages/uvicorn/main.py", line 575, in run
    server.run()
  File "/usr/local/lib/python3.10/dist-packages/uvicorn/server.py", line 65, in run
    return asyncio.run(self.serve(sockets=sockets))
  File "/usr/lib/python3.10/asyncio/runners.py", line 44, in run
    return loop.run_until_complete(main)
  File "/usr/local/lib/python3.10/dist-packages/vllm/engine/async_llm_engine.py", line 470, in engine_step
    request_outputs = await self.engine.step_async()
  File "/usr/local/lib/python3.10/dist-packages/vllm/engine/async_llm_engine.py", line 226, in step_async
    self.stat_logger.log(self._get_stats(scheduler_outputs))
  File "/usr/local/lib/python3.10/dist-packages/vllm/engine/metrics.py", line 229, in log
    logger.info(
Message: 'Avg prompt throughput: %.1f tokens/s, Avg generation throughput: %.1f tokens/s, Running: %d reqs, Swapped: %d reqs, Pending: %d reqs, GPU KV cache usage: %.1f%, CPU KV cache usage: %.1f%'
Arguments: (154.2963163763204, 213.39696198061793, 13, 0, 0, 23.515151515151512, 0.0)

[MahmoudAshraf97]

@simon-mo I don't think this is related to my PR, it was fixed in #4396
I synced my fork and hopefully it will pass the CI

[simon-mo]

Processed prompts: 100%\|██████████\| 1000/1000 [01:02<00:00, 16.10it/s, Generation Speed: 4122.04 toks/s]
 

LGTM!