[ao][sparsity] Fixing failing internal pruner tests (#80111)
After a recent change in the base_sparsifier API, the internal pruner started failing. This adopts the testcases to the change:
1. Changed `module_groups` to `groups`
2. Changed the fusion logic from taking care of the whole fused module to handling the submodules individually.
Differential Revision: [D37364801](https://our.internmc.facebook.com/intern/diff/D37364801/)
**NOTE FOR REVIEWERS**: This PR has internal Facebook specific changes or comments, please review them on [Phabricator](https://our.internmc.facebook.com/intern/diff/D37364801/)!
Pull Request resolved: https://github.com/pytorch/pytorch/pull/80111
Approved by: https://github.com/macandro96
