Support for more Schema types like "anyOf"

## What feature would you like to see?

I would like to see some missing but important schema types like anyOf .

Here are all the schema types for reference: https://cloud.google.com/vertex-ai/generative-ai/docs/multimodal/control-generated-output#fields

Start by locating the Firebase Android SDK code that defines or validates generated-output schemas, then compare its supported types with the linked Vertex AI reference. Clarify which missing schema types, including anyOf, are in scope and identify the tests needed to verify support.

Written by the indexing model from the issue text.