[Docs] Mock all imports for docs

[hmellor]

Special cases that needed handling:

• Make nn.Parameter inheritable when it's mocked
• Make registering a custom op a no-op (decorator and functional)

General improvements:

• If vLLM asks for a package version, get it from requirements/test.txt
• Some runtime imports need mocking too, handle those
• Add if __name__ == "__main__" to make the script easier to test

[mergify]

Documentation preview: https://vllm--27873.org.readthedocs.build/en/27873/

[gemini-code-assist]

Code Review

This pull request introduces a robust mechanism for mocking imports during documentation generation, which significantly improves the developer experience by removing the need for heavy dependencies like PyTorch. The approach to handle runtime imports and special cases for nn.Parameter and custom ops is well-designed. I have identified a minor issue in how package versions are parsed from the requirements file, which could lead to incorrect version strings. My review includes a specific code suggestion to make this parsing more robust. Overall, this is a valuable improvement.

[chatgpt-codex-connector]

💡 Codex Review

Here are some automated review suggestions for this pull request.

ℹ️ About Codex in GitHub

Codex has been enabled to automatically review pull requests in this repo. Reviews are triggered when you

• Open a pull request for review
• Mark a draft as ready
• Comment "@codex review".

If Codex has suggestions, it will comment; otherwise it will react with 👍.

When you sign up for Codex through ChatGPT, Codex can also answer questions or update the PR, like "@codex address that feedback".

[DarkLight1337]

Thanks for simplifying!