Re-enable elastic training for torch 2+ (#4010)
* Switch elasticity function
* Switch elastic training to support torch 2+
* Add comment back in
* Move function to runtime.utils
* Formatting and removing newly unused torch import
* Typo fixed
* Forgot to replace unit with deepspeed.runtime
* Fixes
* Move more functions away from TORCH_MAJOR
* Remove more torch_major
* Fixes
* Remove additional torch_major/minor
