make profiling take no_grad flags into account (#31071)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/31071
Previously the profiler would think Tensors would require grad, even
when the no_grad flag is enabled during execution. This makes the profiling
and guards respect the no_grad flag, which eliminates extra differentiable
graphs that appear in the backward graph (where no_grad is typically enabled).
Test Plan: Imported from OSS
Differential Revision: D18915468
Pulled By: zdevito
fbshipit-source-id: 1ae816a16ab78ae5352825cc6b4a68ed7681a089
