Split of "[TorchRec][PT2] KJT custom op for 1d lengths input" (#2163)

[TroyGarden]

Summary:

X-link: https://github.com/pytorch/FBGEMM/pull/2774

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 on CPU and GPU
• backward/autograd not tested

Differential Revision: D59031938

[facebook-github-bot]

This pull request was exported from Phabricator. Differential Revision: D59031938

[facebook-github-bot]

This pull request has been reverted by b8a1c40a22ca3970f8139d5a79ada8d44b7c7ad1.