feat: groq integration

[joshua-mo-143]

Fixes #145

An attempt was made to use the openai provider module but it looks like each provider module's CompletionModel struct is dependent on each provider's client module rather than a trait, which makes refactoring slightly more complicated.

[0xMochan]

Mainly would want you to reuse the openai's Message struct as it'll vastly improve a future rebase on top of my #199 PR (merging soon). Reusing more structs, the better. Reusing CompletionResponse is max but not always possible!

[joshua-mo-143]

Looks like Groq is like Galadriel in that it doesn't actually follow the OpenAI chat completion API standard. Types will be imported from the Galadriel module.

Nevermind, Groq doesn't support tool_calls in the message. Guess we'll be making our own message type for this.

I've tested that it works locally both in the groq example and the agent_with_tools example (by substituting for the groq module client).

[cvauclair]

@0xMochan have the requested changes been addressed? This PR looks pretty ready to me

[0xMochan]

Looks good, ready to merge!