Remove references to Triton model serving

What does this merge request do and why?

• Remove references to Triton and Codegen model (we no longer support this in the AI Gateway).
• Update the code syntax for environment variables.
• Update system requirements and folder structures.
• Fix outdated VS Code configuration.

How to set up and validate locally

Numbered steps to set up and validate the change are strongly suggested.

Merge request checklist

• Tests added for new functionality. If not, please raise an issue to follow up.
• Documentation added/updated, if needed.