[ENH] Added http_client parameter to OpenAIEmbeddingFunction

[weissgerber1]

Added support for a custom HTTP client in the OpenAIEmbeddingFunction class.

• Added an optional http_client parameter of type httpx.Client to the __init__ method of OpenAIEmbeddingFunction
• Updated the constructor to pass the http_client to both openai.AzureOpenAI and openai.OpenAI when initializing the client for OpenAI SDK v1.x.
• Updated the class docstring with info on http_client

The change allows for providing an own HTTP client. Useful for SSL configuration, proxies or connection pooling.

Backwards compatibility is maintained as the OpenAI client will use its default HTTP client when provided with 'None'.

[github-actions[bot]]

Reviewer Checklist

Please leverage this checklist to ensure your code review is thorough before approving

Testing, Bugs, Errors, Logs, Documentation

• [ ] Can you think of any use case in which the code does not behave as intended? Have they been tested?
• [ ] Can you think of any inputs or external events that could break the code? Is user input validated and safe? Have they been tested?
• [ ] If appropriate, are there adequate property based tests?
• [ ] If appropriate, are there adequate unit tests?
• [ ] Should any logging, debugging, tracing information be added or removed?
• [ ] Are error messages user-friendly?
• [ ] Have all documentation changes needed been made?
• [ ] Have all non-obvious changes been commented?

  System Compatibility

• [ ] Are there any potential impacts on other parts of the system or backward compatibility?
• [ ] Does this change intersect with any items on our roadmap, and if so, is there a plan for fitting them together?

  Quality

• [ ] Is this code of a unexpectedly high quality (Readability, Modularity, Intuitiveness)

[jeffchuber]

Our underlying impl has changed and so this PR is not landable as is.

That being said - we'd still like to add this functionality and that is now tracked in this issue.