[sparsity][refactor] Import factoring out (#58707)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/58707
Minor refactor that changes the format of the import.
This is done to avoid accidental circular dependencies.
Test Plan:
```
python test/test_ao_sparsity.py
```
Imported from OSS
Differential Revision:
D28970961
D28970961
Reviewed By: raghuramank100
Pulled By: z-a-f
fbshipit-source-id: c312742f5e218c435a1a643532f5842116bfcfff
