Nathan unify modelargs (#609)
- removed override batch size and made it part of model config
- remove env config, config should be part of env directly, no need to load it up
- better loading of models
- baseclass for model configs, allows parsing of model config through cli or config file.
- Unified naming for model args, i.e. `model_name`
- removed openai endpoint, we can just use litellm for this, same for TGI and inference endpoints we don't really need it and it's better to have one interface
