Revert "separate out dynamo .requires_grad and .is_grad_enabled guards (#100570)"
This reverts commit 1fabee399d74ee5e1b519673a15619e9fded6562.
Reverted https://github.com/pytorch/pytorch/pull/100570 on behalf of https://github.com/PaliC due to breaking inductor tests along with #101219 ([comment](https://github.com/pytorch/pytorch/pull/100570#issuecomment-1555271267))
