Fixed an issue where base OpenAI embeddings can't work with Azure Ope…

[KennyStryker]

Description

When you try to use base OpenAI embeddings with Azure OpenAI LLM deployment, you can index the document because hydrate_embeddings_params replaced None with Azure OpenAI base_url.

Related Issues

#492

Proposed Changes

This PR fixes the issues, such that all following event work as expected:

• same api_bases for LLM and embeddings (both Azure)
• different api_bases for LLM and embeddings (both Azure)
• LLM uses Azure OpenAI, while embeddings uses base OpenAI (this one is important)
• LLM uses Azure OpenAI, while embeddings uses third-party OpenAI-like API

Checklist

• [X] I have tested these changes locally.
• [x] I have reviewed the code changes.
• [ ] I have updated the documentation (if necessary).
• [ ] I have added appropriate unit tests (if applicable).

Additional Notes

[Add any additional notes or context that may be helpful for the reviewer(s).]