Benefits torch_sparse.SparseTensor compared to torch.sparse.

[kdekker-kdr4]

@rusty1s The package "torch_sparse" is advised to be used in the Advanced Concepts on Memory Efficient Aggregations.
There is however also torch.sparse. It is not clear enough for me what the benefit is (and still is) of using torch_sparse.SparseTensor over creating sparse tensors with torch.sparse.

Noticed (Correct me if I make a wrong statement):

1. The latest release of torch_sparse is now almost 2 years ago, while torch.sparse is kept being developed.
2. I have noticed support for torch.sparse in available GNN.
3. There is support for sparse matrix multiplication in torch now via torch.sparse tensors.