KJT custom op for 1d lengths input

[TroyGarden]

Summary:

context

• move the tensor.view(-1, stride) from python into the operator (c++)
• make the PT2 complier happy
• reference: D58948987

notes

• not sure if we should directly change the op call in the jagged_tensor
• tested in CPU
• backward and GPU haven't tested

Differential Revision: D58956327

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This pull request was exported from Phabricator. Differential Revision: D58956327

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This pull request has been merged in pytorch/FBGEMM@e47a82cba90501a70e836af13b6171417173e883.