Add `tensor_split` function, based on `numpy.array_split` (#45168)
Summary:
Fixes https://github.com/pytorch/pytorch/issues/9382
Pull Request resolved: https://github.com/pytorch/pytorch/pull/45168
Reviewed By: ngimel
Differential Revision: D24166164
Pulled By: mruberry
fbshipit-source-id: 795459821e52885bc99623a01a2abec060995ce6
