[sparsity] Remove the pack_param from the sparsifier state_dict (#65292)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/65292
That was the original design, that we decided to simplify by removing the packing in the sparsifier.
The state of the sparsifier is saved directly, and the old behavior accidentally bled through to the current version.
This change removes the `_pack_params` method, and changes the state_dict to include the state directly.
We don't have to change the load_state_dict, as it will work with either the old or the new format.
The main reason for this PR is the simplification. The original design didn't achieve anything useful by packing the sparsification parameters.
Test Plan: Imported from OSS
Reviewed By: gchanan
Differential Revision: D31186826
Pulled By: z-a-f
fbshipit-source-id: 4ad72a7e669f048d2f2d269269ee11b63fa169db
