[Feature] Add gather/scatter support 1D tensor

[chang-l]

Migrated from: rapidsai/wholegraph#229

This PR is to add gather/scatter support 1D tensor on python level, as WholeGraph should support basic indexing operations for both 1D (array) and 2D (matrix) wholememory tensors. Without this PR, if with 1D wholememory tensor, gather/scatter op does not work, e.g., https://github.com/rapidsai/wholegraph/blob/0efba33835d6e4e104b5d7101a91e0ea55a6ca53/python/pylibwholegraph/pylibwholegraph/torch/tensor.py#L89

To test, run

pytest --cache-clear  --import-mode=append  tests/wholegraph_torch/ops/test_wholegraph_gather_scatter.py -s

Remaining issue:

On my local test with single GPU, the test can pass.
For multiGPU setup, gather op works fine, but 1D scatter seems not working as it would crash at:
https://github.com/rapidsai/wholegraph/blob/2e963b98aa6027c300d60e839010d3dd8ca422eb/python/pylibwholegraph/pylibwholegraph/tests/wholegraph_torch/ops/test_wholegraph_gather_scatter.py#L108 with incorrect scatter outputs: Indices where allclose fails: tensor([0., 0., 0., ..., 0., 0., 0.]) tensor([ 1435., 1439., 1443., ..., 257703., 257707., 257711.])

This would work if this bugfix is merged: #73

cc. @linhu-nv

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[linhu-nv]

Seems good to me. Thx!

[alexbarghi-nv]

/ok to test

[alexbarghi-nv]

@chang-l looks like you have a check style failure here too