[Clean up] Gemini and deepseek with openAI api

[sahel-sh]

Now that Gemini supports openAI API (https://ai.google.dev/gemini-api/docs/openai) we can get rid of the rank_gemini class. We can clean up the SafeOpenAI class and make it work with all three model groups.

[sahel-sh]

Claude models are also compatible with openAI API.
Let's have one class for GPT, Gemini, DeepSeek, and Claude inferences all using openAI API.