unify pool benchmark (#28898)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/28898
as title
Test Plan:
```
buck run mode/opt //caffe2/benchmarks/operator_benchmark/pt:pool_test
# ----------------------------------------
# PyTorch/Caffe2 Operator Micro-benchmarks
# ----------------------------------------
# Tag : short
# Benchmarking PyTorch: MaxPool1d
# Mode: Eager
# Name: MaxPool1d_kernel3_stride1_N8_C256_L256_cpu
# Input: kernel: 3, stride: 1, N: 8, C: 256, L: 256, device: cpu
Forward Execution Time (us) : 7133.492
Reviewed By: hl475
Differential Revision: D18228351
fbshipit-source-id: 47af93d5dd3776384f89b1289fbbe01c572ba9fc
