[NNC] refactor cuda half support to more general file (#47373)
Summary: Pull Request resolved: https://github.com/pytorch/pytorch/pull/47373
Test Plan: Imported from OSS
Reviewed By: ansley
Differential Revision: D24805246
Pulled By: eellison
fbshipit-source-id: 33b5c84c9212d51bac3968e02aae2434dde40cd8
