[Feature] support workers when using lite autoawq

### Motivation

Hi all. @lvhan028 @lzhangzz @AllentDan When I want to use `lite autoawq` with Llama 3.1 405B Instruct, it takes a very long time.

```bash
python3 -m lmdeploy lite auto_awq Meta-Llama-3.1-405B-Instruct
```

May we support `--workers` similar to TensorRT LLM? Thanks.

ref https://nvidia.github.io/TensorRT-LLM/performance/perf-overview.html#engine-building

> --workers affects the number of threads that build the engine file and does not necessarily need to match the TP size.

### Related resources

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### Additional context

_No response_