Add PyTorch 2.0 to ORT transformer benchmarking (#14300)
### Description
This PR adds PyTorch 2.0 as an option when running the ORT transformer
benchmarking script.
### Motivation and Context
PyTorch released [PyTorch
2.0](https://pytorch.org/get-started/pytorch-2.0/) in the nightly
binaries and a stable release of PyTorch 2.0 is expected in March 2023.
