Spring-ai GH-981: Use OpenAIAsyncClient for streaming in AzureOpenAiChatModel

Resolves https://github.com/spring-projects/spring-ai/issues/981

• Switch to OpenAIAsyncClient for streaming operations
• Modify AzureOpenAiChatModel constructor to accept OpenAIClientBuilder
• Update getChatCompletionsStream to use non-blocking async client
• Refactor related classes and tests to support OpenAIClientBuilder
• Revise AzureOpenAiAutoConfiguration to provide OpenAIClientBuilder
• Add AzureOpenAiChatClientTest to verify streaming functionality
• Adjust existing tests for compatibility with OpenAIClientBuilder

Comment From: markpollack

merged in ef3d43ca9cd5c24b34af1c4d536eb2c522c998bb