Add helpers to disable progress bars globally + tests (#987)
* Add helpers to disable progress bars globally + tests
* code quality + docstring
* make value optional in _is_true
* Update src/huggingface_hub/utils/tqdm.py
Co-authored-by: Sylvain Gugger <35901082+sgugger@users.noreply.github.com>
* Env variable has priority over code to disable tqdm
* style
Co-authored-by: Sylvain Gugger <35901082+sgugger@users.noreply.github.com>