accelerate deepspeed and gradient accumulation integrate (#23236)

* mixed precision support via accelerate

* fix issues

* fix for the sharded ddp case

* fix flax and tf failing tests

* `refactor the place to create `Accelerator` object

* move ddp prep to accelerate

* fix 😅

* resolving comments

* move fsdp handling to accelerate

* fixex

* fix saving

* shift torch dynamo handling to accelerate

* shift deepspeed integration and save & load utils to accelerate

* fix accelerate launcher support

* oops

* fix 🐛

* save ckpt fix

* Trigger CI

* nasty 🐛 😅

* as deepspeed needs grad_acc fixes, transfer grad_acc to accelerate

* make tests happy

* quality ✨

* loss tracked needs to account for grad_acc

* fixing the deepspeed tests

* quality ✨

* 😅😅😅

* tests 😡

* quality ✨

* Trigger CI

* resolve comments and fix the issue with the previous merge from branch

* Trigger CI

* accelerate took over deepspeed integration

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Co-authored-by: Stas Bekman <stas@stason.org>