[sparsity] sparsifier `convert` tests (#60105)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/60105
Unit tests for sparsifier `convert`
Test Plan:
`buck test mode/dev-nosan //caffe2/test:ao -- TestWeightNormSparsifier`
https://pxl.cl/1LhQ8
Reviewed By: z-a-f
Differential Revision: D29145450
fbshipit-source-id: b87b8f0d44751a7dae19d454a11b2d207a7286e2
