unify unary ops benchmark (#28913)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/28913
as title
Test Plan:
```
buck run mode/opt //caffe2/benchmarks/operator_benchmark/pt:unary_test
# ----------------------------------------
# PyTorch/Caffe2 Operator Micro-benchmarks
# ----------------------------------------
# Tag : short
# Benchmarking PyTorch: abs
# Mode: Eager
# Name: abs_M512_N512_cpu
# Input: M: 512, N: 512, device: cpu
Forward Execution Time (us) : 90.233
...
Reviewed By: hl475
Differential Revision: D18231641
fbshipit-source-id: 3093db47d0356b927768f15dc63af6ad8aadd430
