C++ C2/Glow operator unittest
Summary: Pull Request resolved: https://github.com/pytorch/pytorch/pull/32258
Test Plan:
```
buck test glow/fb/test/numerics:fp16_op_test
```
Reviewed By: bddppq
Differential Revision: D19401786
fbshipit-source-id: 1382b5208be6172d3e6f768dedad7ebec31cffc9
