Support latest Google Unified SDK to access Google AI Embedding Models

[ddobrin]

This is a placeholder EPIC issue to support https://ai.google.dev/gemini-api/docs/embeddings.

New embedding model release announcement https://developers.googleblog.com/en/gemini-embedding-available-gemini-api/

All previous threads/issues of discussion should be consolidated into this issue.

[misselvexu]

/attempt ?

[ddobrin]

I will provide a PR by end of week