add dim to the cat benchmark (#27620)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/27620
as title
Test Plan:
```
buck run caffe2/benchmarks/operator_benchmark/pt:cat_test -- --iterations 3
# ----------------------------------------
# PyTorch/Caffe2 Operator Micro-benchmarks
# ----------------------------------------
# Tag : short
# Benchmarking PyTorch: cat
# Mode: Eager
# Name: cat_M256_N512_K1_dim0
# Input: M: 256, N: 512, K: 1, dim: 0
Forward Execution Time (us) : 775.348
# Benchmarking PyTorch: cat
# Mode: Eager
# Name: cat_M256_N512_K1_dim1
# Input: M: 256, N: 512, K: 1, dim: 1
Forward Execution Time (us) : 3612.599
# Benchmarking PyTorch: cat
# Mode: Eager
# Name: cat_M256_N512_K1_dim2
# Input: M: 256, N: 512, K: 1, dim: 2
Forward Execution Time (us) : 91416.224
...
``
Reviewed By: hl475
Differential Revision: D17835348
fbshipit-source-id: 94e02e328c4ea61b2e210d860ccdd377ef2b97f8
