Add Matscipy Neighborlist Support

[tgmaxson]

For my test case, this implementation was slightly faster than the pymatgen neighborlist but I did not extensively test this.

from matscipy.neighbours import neighbour_list

def calc_neighbor_by_matscipy(
    pos: Tensor, cell: Tensor, pbc: Tensor, cutoff: float
) -> Tuple[Tensor, Tensor]:
    idx_i, idx_j, S = neighbour_list(
        quantities="ijS",
        pbc=pbc.detach().cpu().numpy(),
        cell=cell.detach().cpu().numpy(),
        positions=pos.detach().cpu().numpy(),
        cutoff=cutoff,
    )
    edge_index = torch.tensor(np.stack([idx_i, idx_j], axis=0), dtype=torch.int64, device=pos.device)
    # convert int64 -> pos.dtype (float)
    S = torch.tensor(S, dtype=pos.dtype, device=pos.device)
    return edge_index, S

[corochann]

Thank you for opening the issue and sharing the codes.

Recently I have no time to include it in main branch, but it is helpful information for others!