[FEATURE] Add support for Google Gemini API

[boapps]

Is your feature request related to a problem? Please describe. Google AI models can be used with their genai library. I think it would be nice to have support for this as an alternative API.

Describe the solution you'd like Add a new GoogleAILLM which allows using their API platform as an LLM.

Describe alternatives you've considered I know it's possible to use Vertex AI, but if I understand it correctly that's mostly for enterprise uses. While this is more for hobby projects. Also has different pricing.

Additional context I'll have an attempt at this, expect a PR soon.