feature -- LiteLLM integration for Ecologits

[cvarrei]

Integration added for the LiteLLM proxy-like library. This library standardises LLM API calls across the OpenAI pattern. This makes it easier to integrate LLMs calling into production.

Done -
I have adapted the documentation, made the LiteLLM tracer, add the corresponding tests, add the instrumentor, and adapted the retrieval of information for calculating the impact to suit LiteLLM without affecting the other tracers.

I have also updated the TOML for dependencies. As LiteLLM relies on all the current main organisations, when initialising litellm in the script, it will initialise all the ecologits instruments. Thus, the user has to install all the other libraries (openai, mistralai, etc.).

Missing - (I'm leaving it open for you to edit, to make it easier for you to adapt the changes to your needs):

• Updating poetry.lock As you are currently making changes, it will be easier for you to achieve the update with your current changes. The TOML has been modified to make it easier for you.
• cassettes: I've had several raised errors using it, but my tests without it have been successful. I think it will be easier for you to adapt it to your testing strategy.

Congratulations on this project, it's been great to be able to contribute to it.

[adrienbanse]

@cvarrei Many thanks for your PR! 🥳

I made some modifications:

• I updated LiteLLM
• I took care of the lock and cassettes (although I had to change the OpenAI model since I don't have credits anymore - @samuelrince you can re-change this if you wish)
• I integrated your .md doc file in the documentation
• I removed all the dependencies as I don't think that it's needed (they are in the dependencies of LiteLLM no?) - please check if your OK with this 529794e

I still just have one doubt about line 40 of model_repository.py

Thanks!!