MS-AMP support (w/o FSDP) (#3093)
* MS-AMP support sans FSDP
* Fix import
* Fixings
* Last Benjamin nit
* New ruff version cleaning
* Update src/accelerate/accelerator.py
Co-authored-by: Marc Sun <57196510+SunMarc@users.noreply.github.com>
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Co-authored-by: Marc Sun <57196510+SunMarc@users.noreply.github.com>
