Expose azure_ad_token_provider argument to support token expiration

[gregory-shklover]

Description

Expose openai.AzureADTokenProvide attribute for AzureOpenAI models (LLM and embedding).
Corresponding "azure_ad_token_provider" callback can handle token expiration, which is not handled otherwise.

Fixes # (issue)
No separate issue submitted.

New Package?

No

Version Bump?

Did I bump the version in the pyproject.toml file of the package I am updating? (Except for the llama-index-core package)

• Yes
• No

Type of Change

Please delete options that are not relevant.

• New feature (non-breaking change which adds functionality)

How Has This Been Tested?

Please describe the tests that you ran to verify your changes. Provide instructions so we can reproduce. Please also list any relevant details for your test configuration

• Ran manual testing in within private azure-hosted deployment

Suggested Checklist:

• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I have added Google Colab support for the newly added notebooks.
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• I ran make format; make lint to appease the lint gods