shift torch dynamo handling to accelerate (#23168)
* 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
