Don't support doubao1.6

Volcano Engine offers two authentication methods:

1. API Key signature authentication
2. Access Key signature authentication

Volcano Engine models provide three types of interfaces:

1. Data plane API
2. Control plane API
3. Base URL

Interfaces such as ListFoundationModels belong to the control plane API, which only supports Access Key signature authentication. However, this module only supports API Key signature authentication, therefore it cannot use ListFoundationModels or similar methods to retrieve the model list.

Another issue to support access_key signature needs be created.

Fix the text to image model

Embeddings model support