Refresh callable Azure API keys before requests

[LittleChenLiya]

Summary

Fix Azure clients so callable api_key providers are refreshed before each request.

AzureOpenAI and AsyncAzureOpenAI override _prepare_options() to add Azure-specific auth headers, but they were not refreshing callable API keys before setting the api-key header. As a result, dynamic API key providers were not applied to requests or retries.

Changes

• refresh callable API keys at the start of AzureOpenAI._prepare_options()
• refresh callable API keys at the start of AsyncAzureOpenAI._prepare_options()
• add sync and async regression tests covering callable api_key providers across retries

Testing

• python -m pytest tests/lib/test_azure.py -n 0
• python -m pytest tests/test_client.py -k "api_key_before_after_refresh or api_key_refresh_on_retry or bearer_token_refresh_async" -n 0

Closes #2626

[chatgpt-codex-connector]

💡 Codex Review

Here are some automated review suggestions for this pull request.

Reviewed commit: 1a67dbb199

ℹ️ About Codex in GitHub

Codex has been enabled to automatically review pull requests in this repo. Reviews are triggered when you

• Open a pull request for review
• Mark a draft as ready
• Comment "@codex review".

If Codex has suggestions, it will comment; otherwise it will react with 👍.

When you sign up for Codex through ChatGPT, Codex can also answer questions or update the PR, like "@codex address that feedback".