Refactor LLM settings

[marginal23326]

I moved all LLM provider configs (base url, default model names, etc.), into a single dict PROVIDER_CONFIGS.

This should clean up utils.py (especially the get_llm_model function), and make it easier to add new providers.

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[vvincent1234]

hello, thanks for your PR. refactor PRs need to be reviewed later, because it gets time to test all over

[marginal23326]

hello, thanks for your PR. refactor PRs need to be reviewed later, because it gets time to test all over

Got it, thanks for the notice.

[marginal23326]

Hi, @warmshao.

Could you review this PR when possible?

Thanks

[warmshao]

Thank you @marginal23326 for this well-organized refactoring of the LLM settings. Centralizing the provider configurations into a single dictionary is a great step towards improving code maintainability and simplifying the addition of new providers. This change should make the get_llm_model function much cleaner and easier to manage.

The modifications in the test suite and environment file also seem well-aligned with the refactoring goals. We appreciate your contribution, and the maintainers will review the code shortly.