[StaticRuntime][ATen] Add out variant for narrow_copy (#49449)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/49449
Similar to permute_out, add the out variant of `aten::narrow` (slice in c2) which does an actual copy. `aten::narrow` creates a view, however, an copy is incurred when we call `input.contiguous` in the ops that follow `aten::narrow`, in `concat_add_mul_replacenan_clip`, `casted_batch_one_hot_lengths`, and `batch_box_cox`.
{F351263599}
Test Plan:
Unit test:
```
buck test //caffe2/aten:native_test
```
Benchmark with the adindexer model:
```
bs = 1 is neutral
Before:
I1214 21:32:51.919239 3285258 PyTorchPredictorBenchLib.cpp:209] PyTorch run finished. Milliseconds per iter: 0.0886948. Iters per second: 11274.6
After:
I1214 21:32:52.492352 3285277 PyTorchPredictorBenchLib.cpp:209] PyTorch run finished. Milliseconds per iter: 0.0888019. Iters per second: 11261
bs = 20 shows more gains probably because the tensors are bigger and therefore the cost of copying is higher
Before:
I1214 21:20:19.702445 3227229 PyTorchPredictorBenchLib.cpp:209] PyTorch run finished. Milliseconds per iter: 0.527563. Iters per second: 1895.51
After:
I1214 21:20:20.370173 3227307 PyTorchPredictorBenchLib.cpp:209] PyTorch run finished. Milliseconds per iter: 0.508734. Iters per second: 1965.67
```
Reviewed By: bwasti
Differential Revision: D25554109
fbshipit-source-id: 6bae62e6ce3456ff71559b635cc012fdcd1fdd0e
