Allow customization of `parallel_tool_calls` request parameter for function calling

[dnflow]

I upgrade to the latest 8.6.1, from v7 . And instead of passing functions, I now have to pass in Tools. One of the benefits of tools, is that it allows parallel processing. But in my case I do not want parallel processing.

I would like to simply be able to set this value ex:

var request = new ChatCompletionCreateRequest() {
...
ParallelToolCalls = false,
...
}

the request to OpenAi should include { parallel_tool_calls: false }

More info from OpenAI https://platform.openai.com/docs/guides/function-calling/parallel-function-calling