Use passed --cache_dir for modules cache
When passed `--cache_dir` arg:
```shell
python datasets-cli test datasets/<my-dataset-folder> --save_infos --all_configs --cache_dir <my-cache-dir>
```
it is not used for caching the modules, which are cached in the default location at `.cache/huggingface/modules`.

With this fix, the modules will be cached at `<my-cache-dir>/modules`.