Various magic enhancements and fixes

[dlqqq]

• Fix HF Hub provider not respecting the model_id kwarg
  • This is because weirdly enough, the repo_id attribute used by the upstream provider implementation is not resolved dynamically (i.e. self.repo_id is not accessed on model invocation); it is set statically in the constructor like so:

@root_validator()
    def validate_environment(cls, values: Dict) -> Dict:
        """Validate that api key and python package exists in environment."""
        huggingfacehub_api_token = get_from_dict_or_env(
            values, "huggingfacehub_api_token", "HUGGINGFACEHUB_API_TOKEN"
        )
        try:
            from huggingface_hub.inference_api import InferenceApi

            repo_id = values["repo_id"]
            client = InferenceApi(
                repo_id=repo_id,
                token=huggingfacehub_api_token,
                task=values.get("task"),
            )
        ...

• Improve magics documentation
• Add [all] optional dependency group to easily install all model provider dependencies