Add tensor-scalar op (#62903)
Summary: Pull Request resolved: https://github.com/pytorch/pytorch/pull/62903
Test Plan: Imported from OSS
Reviewed By: pbelevich, SplitInfinity
Differential Revision: D30168338
Pulled By: eellison
fbshipit-source-id: 7dcb34ddd76c6aad4108a4073d3c8a93d974d0ef
