Add RAII DetectAnomalyGuard (#47164)
Summary:
This is a followup to the C++ anomaly detection mode, implementing the guard.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/47164
Reviewed By: mruberry
Differential Revision: D24682574
Pulled By: albanD
fbshipit-source-id: b2224a56bf6eca0b90b8e10ec049cbcd5af9d108
