Option to pull all model information live

Goal: Goose should have an option to pull all model information (context limits, modalities) from a live source instead of the existing pre-built canonical_models.json. You shouldn't need to update goose to get support for a new model's canonical info. (There still may be updates required for new models as they may include API changes, but that is not always the case.)

Some options:
- pull directly from models.dev live
- pull a live version of our existing canonical_models.json
- shift to querying all of this directly from providers