* fix: `nb` is set total number of devices, when nb is -1.
Refs: #4207
* feat: add test code
1. test combination `auto_select_gpus`, `gpus` options using
Trainer
2. test `pick_multiple_gpus` function directly
Refs: #4207
* docs: modify contents in `Select GPU devices`
Refs: #4207
* refactore: reflect the reuslt of review
Refs: #4207
* refactore: reflect the reuslt of review
Refs: #4207
* Update CHANGELOG.md
Co-authored-by: chaton <thomas@grid.ai>
Co-authored-by: Roger Shieh <55400948+s-rog@users.noreply.github.com>
Co-authored-by: Nicki Skafte <skaftenicki@gmail.com>
Jirka Borovec