[sparsity] WeightNormSparsifier (#58955)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/58955
Implements the weight norm sparsifier.
This type of sparsifier computes the norm of the weights, sorts them, and zeroes-out the target fraction of them.
The main imeplemented method is `update_mask`, which holds the main logic of changing the masks.
Test Plan:
```
python test/test_ao_sparsity.py
```
Imported from OSS
Differential Revision:
D28970960
D28970960
Reviewed By: raghuramank100
Pulled By: z-a-f
fbshipit-source-id: 8f2a4360ad877f430cdc1065c6777106938b58d5
