Python: Support OpenAI message "name" field

[gdhuang]

Background
The Python SDK does not currently map the ChatMessage.author_name field to OpenAI's optional "name" field when sending messages to the OpenAI completion API.
This field is useful for identifying different participants in conversations.

Current Behavior
In the Python implementation, the ChatMessage class has an author_name attribute.
However, when converting messages to OpenAI format in _openai_chat_message_parser(), the author_name is not included:
File: python/packages/core/agent_framework/openai/_chat_client.py:364-393

Expected Behavior

The author_name should be mapped to OpenAI's "name" field when present, similar to how the .NET implementation handles it.

string? name = SanitizeAuthorName(input.AuthorName);

File: https://github.com/dotnet/extensions/blob/main/src/Libraries/Microsoft.Extensions.AI.OpenAI/OpenAIChatClient.cs:158