Support CSR to COO conversion in to_sparse(2). (#73642)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/73642
Former https://github.com/pytorch/pytorch/pull/73471 that was reverted due to lack of `to_sparse(sparse_dim)` support.
Test Plan: Imported from OSS
Reviewed By: zou3519
Differential Revision: D34580353
Pulled By: cpuhrsch
fbshipit-source-id: a8a4ea381daeb80d8365fe931af9f55a7e789ea1
(cherry picked from commit 5a3cf8110980e5a10dbb687e87e67d5524ebf2f5)
