Improve Code Llama documentation with explanations and helpful links

[PrakyathMC]

What does this PR do?

Improves the Code Llama model documentation following the standardized format outlined in #36979.

Changes Made

• ✅ Added explanatory comments to code examples explaining imports and parameters
• ✅ Added "Quick Links" section with popular Code Llama models on HuggingFace Hub
• ✅ Included additional resources (paper links, model collection)
• ✅ Improved accessibility for beginners learning to use Code Llama

Before and After

Before: Basic code examples without explanations
After: Commented code that teaches users what each line does + easy access to models

Fixes #36979

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 or the forum? Please add a link
  to it if that's the case.
• Did you make sure to update the documentation with your changes? Here are the
  documentation guidelines, and
  here are tips on formatting docstrings.
• 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.

[stevhliu]

CodeLlama has already been updated in #37115!