feat: add optional `chat_name` and `embedding_name` fields in `config.json`

[apepkuss]

Major changes:

• Introduce chat_name and embedding_name fields into config.json. The two fields are optional.
• Update CLI tool for extracting model names:
  • If chat_name/embedding_name is present, and the value is not empty, then use the value as the name of the corresponding model;
  • Otherwise, extract the model name from chat/embedding field.