[dte] fastpath implementation for broadcast utility function (4/x) (#62493)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/62493
This diff adds a broadcast fastpath for the caffe2 broadcast utility function, which just copies the contents of a smaller tensor into a larger one. We also update the tests to exercise the new functionality.
Test Plan: unit tests + let CI run
Differential Revision: D29938285
fbshipit-source-id: 543ecc548500380e307be91902696033454964a2
