[pruner] refactor `ActivationReconstruction` forward hooks (#63158)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/63158
Combined functionality for `ActivationReconstruction` for both Linear and Conv2d in one class. The only difference between the old classes was the size and indexing of the reconstructed tensor -- that logic can be generalized by iterating over the size of `output`.
ghstack-source-id: 136467465
Test Plan:
`buck test mode/dev-nosan //caffe2/test:ao -- TestBasePruner`
https://pxl.cl/1MSSv
Reviewed By: raghuramank100
Differential Revision: D30282765
fbshipit-source-id: 08a1e4e0650511019fff85cf52b41dd818b0c7f8
