[DeepSpeed] decouple `DeepSpeedConfigHF` from `Trainer` (#11966)
* decouple DeepSpeedConfigHF from Trainer
* add LoggingLevel ctx manager; add new test
* cleanup
* add docs
* Apply suggestions from code review
Co-authored-by: Sylvain Gugger <35901082+sgugger@users.noreply.github.com>
* implemented suggested renames
* formatter workaround
Co-authored-by: Sylvain Gugger <35901082+sgugger@users.noreply.github.com>