Dynamo benchmark: add CPU specific changes (#88477)
This pr adds some CPU specific changes:
- Add support for IPEX backend
- https://github.com/pytorch/torchdynamo/issues/1618
- https://github.com/pytorch/torchdynamo/issues/1534
- Enable CPU launcher in runner.py.
- Fix the issue that some environment variables are not support on CPU
Pull Request resolved: https://github.com/pytorch/pytorch/pull/88477
Approved by: https://github.com/jgong5, https://github.com/jansel
