Fix the API for record observer (#26413)
Summary:
Mainly want to resolve comments from https://github.com/pytorch/pytorch/pull/25830.
Overall, we want to provide a recording observer for recording the runtime tensor values of activation path in order to debug the numerical accuracy loss offline.
According to the feedback from https://github.com/pytorch/pytorch/issues/25830, it might be better to record all the observers in a dict and query the dict to get corresponding tensor values. hx89 is working on how to insert the recording observers into model under debug.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/26413
Differential Revision: D17506502
Pulled By: llyfacebook
fbshipit-source-id: 3ab90dc78920e7ec3fa572c2a07327a9991c530a
