Extend CLI to orpo trainer

[murilo-cunha]

What does this PR do?

Thanks for the cool project! Happy to learn more and contribute!

This adds CLI support to the ORPO trainer. This is heavily inspired by the scripts in experimental/scripts/ and what was done for the other trainers, especially the KTO trainer (including the tests).

Didn't add any documentation, cause it wasn't clear if it's applicable for CLI extensions.

Fixes (partially) #2101

Before submitting

• This PR fixes a typo or improves the docs (you can dismiss the other checks if that's the case).
• Did you read the contributor guideline,
  Pull Request section?
• Was this discussed/approved via a GitHub issue? Please add a link
  to it if that's the case.
• Did you make sure to update the documentation with your changes?
• Did you write any new necessary tests?

Who can review?

Anyone in the community is free to review the PR once the tests have passed. Feel free to tag
members/contributors who may be interested in your PR.