fix bug to add large tensor support

[kaixuanliu]

No description provided.

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 11 lines in your changes are missing coverage. Please review.

Project coverage is 86.40%. Comparing base (0ae8cdf) to head (ec46153).

Files	Patch %	Lines
pyg_lib/csrc/ops/cpu/radix_sort.h	0.00%	11 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #308      +/-   ##
==========================================
- Coverage   86.47%   86.40%   -0.08%     
==========================================
  Files          35       35              
  Lines        1213     1214       +1     
==========================================
  Hits         1049     1049              
- Misses        164      165       +1     

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[kaixuanliu]

I ran into an error as I define a very large sparse tensor in the following code,
`import torch
import torch_sparse

num_edges = 7982968874
num_src_nodes = 264388606
edge_id = torch.arange(num_edges, dtype=torch.int64)
node_sizes = (num_src_nodes + 1, num_src_nodes + 1)
row = torch.randint(num_src_nodes, (num_edges, ), dtype=torch.int64)
col = torch.randint(num_src_nodes, (num_edges, ), dtype=torch.int64)
adj_t = torch_sparse.SparseTensor(
row=row, col=col, value=edge_id, sparse_sizes=node_sizes
)`

It will crash in the former implementation due to incorrect data type conversion, this PR solved this kind of data overflow

[rusty1s]

Thank you:)