Extend some of the basic ops to kHalf (#37121)
Summary:
Added enough operators to make sure that all unit tests from ATen/basic are passing, except for MM and IntArrayRefExpansion
Pull Request resolved: https://github.com/pytorch/pytorch/pull/37121
Test Plan: `./bin/basic --gtest_filter=--gtest_filter=BasicTest.BasicTestHalfCPU` + `python -c "import torch; x = torch.tensor([2], dtype=torch.half); print(torch.isfinite(x+x))"`
Differential Revision: D21296863
Pulled By: malfet
fbshipit-source-id: e03d7a6939df11f611a9b317543bac52403cd009
