Improve help in chat UI settings panel for Hugging Face Hub, SageMaker endpoints

[JasonWeill]

Problem

The user interface associated with the chat UI displays '*' as a generic catchall for model IDs associated with Hugging Face Hub and SageMaker endpoints. Users may not be aware of how to find their model ID.

Proposed Solution

When the user selects Hugging Face Hub or SageMaker endpoints as their language model provider, show help in the panel about how to find a model ID.

Additional context

#254 updated the docs and the magic commands with additional info about how to find model IDs for these two providers.