Sparse CSR CUDA: add batched support for torch.sparse.sampled_addmm
This PR adds a forloop around cuSPARSE calls to support batched inputs.
cuSPARSE function itself doesn't support batched inputs yet.
`mat1` and `mat2` must have the same batch shape. It's allowed to pass
`self` as a single matrix when `mat1` and `mat2` are batched.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/77243
Approved by: https://github.com/cpuhrsch
