Fix loading of qwen safetensors

[mokeyish]

Motivation

Fix loading of qwen safetensors. The latest Qwen use safetensors.

https://huggingface.co/Qwen/Qwen-7B-Chat/tree/main

Modification

if load nothing of *.bin, then load *.safetensors.

Checklist

1. Pre-commit or other linting tools are used to fix the potential lint issues.
2. The modification is covered by complete unit tests. If not, please add more unit tests to ensure the correctness.
3. If the modification has a dependency on downstream projects of a newer version, this PR should be tested with all supported versions of downstream projects.
4. The documentation has been modified accordingly, like docstring or example tutorials.

[lvhan028]

Hi, @mokeyish
Thanks for your contribution to lmdeploy. But unfortunately, this PR and PR #482 are duplicates. And we plan to integrate #482 since it is earlier

[mokeyish]

Hope to merge it soon.