[sparsity][refactor] Restructure the tests folders (#60032)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/60032
There will be more sparse tests coming. This PR creates a separate folder for the sparse tests
Test Plan: `python test/test_ao.py`
Reviewed By: raghuramank100
Differential Revision: D29139265
fbshipit-source-id: d0db915f00e6bc8d89a5651f08f72e362a912a6b
