Sparse CSR CPU: add `torch.add` with all inputs sparse (#64391)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/64391
This PR adds `torch.add(a, b, alpha=None, out=out)` variant with `a, b, out` all being sparse CSR tensors on CPU.
Fixes #59060
cc nikitaved pearu cpuhrsch IvanYashchuk
Test Plan: Imported from OSS
Reviewed By: jbschlosser
Differential Revision: D32316562
Pulled By: cpuhrsch
fbshipit-source-id: 384462369007854b5e2e6cb9ae7b320302627c71
