Implement DistributedPyTorchModel

[shaahji]

Description

Implement DistributedPyTorchModel

DistributedPyTorchModel is parallel to DistributedOnnxModel for PyTorch models.
Also, introducing an example, Llama2, as an use case.

Checklist before requesting a review

• Add unit tests for this change.
• Make sure all tests can pass.
• Update documents if necessary.
• Format your code by running pre-commit run --all-files
• Is this a user-facing change? If yes, give a description of this change to be included in the release notes.

(Optional) Issue link

[github-advanced-security]

lintrunner found more than 10 potential problems in the proposed changes. Check the Files changed tab for more details.

[jambayk]

The lintrunner instructions are at https://github.com/microsoft/Olive/blob/main/CONTRIBUTING.md#linting

I find the MYPY linter to be slow, so I skip it using the following:

lintrunner --skip MYPY -a