[pruning] Base pruner class (#60278)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/60278
Implemented `PruningParametrization`, which removes pruned rows, and `BasePruner`, which is the base class for structured pruning.
Test Plan:
`buck test mode/dev-nosan //caffe2/test:ao -- TestBasePruner`
https://pxl.cl/1KC2n
Reviewed By: z-a-f
Differential Revision: D29208349
fbshipit-source-id: f34e8e258bf13fa80292c2bd64d56f5ad1e72b6a
