Add ModelLister for Ollama, Anthropic, Mistral, OpenAI, Gemini

[LHelge]

Summary

Continued on the work from #1075 which introduced the primitives to access the API for listing models. I have implemented the ModelLister trait for the providers that I currently use in my project.

• Ollama
• Anthropic
• Mistral
• OpenAI

Usage

For the providers that has this implementation the list_models() function should be available on the Client

#[tokio::main]
async fn main() -> Result<(), anyhow::Error> {
    let client = anthropic::Client::new("sk-ant-...").unwrap();
    let models = client.list_models().await?;
    println!("Available models: {models:#?}");

    Ok(())
}

Future work

Should be fairly straight forward to copy/paste or vibe the same solution for the remaining providers.

[gold-silver-copper]

Added gemini support as well as tests.