udpated openai-chat + openai-asst c# templates

[robch]

This if the first of several PRs to embrace the new OpenAI branded C# library (and it's Azure friends):

• Updated openai-chat template (shows non-streaming use)
• Updated openai-chat-streaming (shows streaming use)
• Updated openai-chat-streaming-with-data (shows use w/ OYD)
• Updated openai-chat-streaming-with-functions (shows use w/ function tool calling)
• Added openai-asst template (shows non-streaming use)
• Added openai-asst-streaming template (shows streaming use)
• Added openai-asst-streaming-with-code template (shows use w/ code interpretter)
• Added openai-asst-streaming-with-file-search template (shows use w/ file search)
• Added openai-asst-streaming-with-functions (shows use w/ function tool calling)

Use these to instantiate above:

• ai dev new openai-chat --cs
• ai dev new openai-chat-streaming --cs
• ai dev new openai-chat-streaming-with-data --cs
• ai dev new openai-chat-streaming-with-functions --cs
• ai dev new openai-asst --cs
• ai dev new openai-asst-streaming --cs
• ai dev new openai-asst-streaming-with-code --cs
• ai dev new openai-asst-streaming-with-file-search --cs
• ai dev new oepnai-asst-streaming-with-functions --cs