Implemented torch.inner (#46716)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/46716
Implemented torch.inner similar to [numpy.inner](https://numpy.org/doc/stable/reference/generated/numpy.inner.html). For now it's implemented as a composite op.
TODO
- [x] Add documentation
Test Plan: Imported from OSS
Reviewed By: malfet
Differential Revision: D24860351
Pulled By: heitorschueroff
fbshipit-source-id: de5c82f285893495491fdba73b35634f4d00bac8
