feat: LLM-based evaluators return meta info from OpenAI

[davidsbatista]

Related Issues

• fixes #7905

Proposed Changes:

pass the meta entry from openai api to the result for all the LLM-based evaluators, containing the following fields:

• model
• prompt tokens
• answer tokens
• total tokens

How did you test it?

manual veritifcation + run local tests + end2endtests

Checklist

• I have read the contributors guidelines and the code of conduct
• I have updated the related issue with new insights and changes
• I added unit tests and updated the docstrings
• I've used one of the conventional commit types for my PR title: fix:, feat:, build:, chore:, ci:, docs:, style:, refactor:, perf:, test:.
• I documented my code
• I ran pre-commit hooks and fixed any issue