[JIT] scripting, freezing, serialization for sparse csr (#69555)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/69555
1. Implement pickling/unpickling
2. Add `test_freeze_sparse_csr, tests_serialize_sparse_csr` tests
Test Plan: Imported from OSS
Reviewed By: mruberry
Differential Revision: D33181367
Pulled By: davidberard98
fbshipit-source-id: a15d5193a7b1b1625a27e4af003cec33cdbc8071
