rename _min_max to _aminmax (#44001)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/44001
This is to align with the naming in numpy and in
https://github.com/pytorch/pytorch/pull/43092
Test Plan:
```
python test/test_torch.py TestTorchDeviceTypeCPU.test_aminmax_cpu_float32
python test/test_torch.py TestTorchDeviceTypeCUDA.test_aminmax_cuda_float32
```
Imported from OSS
Reviewed By: jerryzh168
Differential Revision: D23465298
fbshipit-source-id: b599035507156cefa53942db05f93242a21c8d06
