.Net OpenAIPromptExecutionSettings ChatSystemPrompt ignored

[Jenscaasen]

Describe the bug
When setting the ChatSystemPrompt property of OpenAIPromptExecutionSettings, it is not used as SystemPrompt

To Reproduce
See code below to reproduce

Expected behavior
The ChatSystemPrompt to be used as SystemPrompt, or renaming of ChatSystemPrompt in case it has a different usage

Platform
.NET, SK 1.0.1

Additional context

 var builder = Kernel.CreateBuilder();
 builder.AddAzureOpenAIChatCompletion([...]);    
var kernel = builder.Build();

 AzureOpenAIChatCompletionService service = (AzureOpenAIChatCompletionService)kernel.Services.GetService(typeof(IChatCompletionService));

 string systemPrompt = "You are batman. If asked who you are, say 'I am Batman!'";

 OpenAIPromptExecutionSettings settings = new() { ChatSystemPrompt = systemPrompt };
 ChatHistory history = new ChatHistory();

 history.AddUserMessage("Who are you?");
     
 ChatMessageContent result = await service.GetChatMessageContentAsync(history, settings, kernel);          
 Console.WriteLine(result.ToString()); //Not Batman

 ChatHistory history2 = new ChatHistory(systemPrompt);
 history2.AddUserMessage("Who are you?");

 ChatMessageContent result2 = await service.GetChatMessageContentAsync(history2, settings, kernel);
 Console.WriteLine(result2.ToString()); //Batman

[brandonh-msft]

Similar repro w/o usage of ChatHistory:

var settings = new OpenAIPromptExecutionSettings
{
    ChatSystemPrompt = "You are batman. If asked who you are, say 'I am Batman!'"
};

await foreach (StreamingKernelContent s in k.InvokePromptStreamingAsync(userPrompt, new(settings)))
{
    Console.Write(s);
}

Intercepting HTTP Client messages will show the following getting sent to the OpenAI endpoint:

{
	"messages": [
		{
			"content": "<userPrompt>",
			"role": "system" // <<<<<--- this should not be 'system', and the 'System' message should be in this array
		}
	],
...
}

seems related to #4377

[dmytrostruk]

@brandonh-msft Thanks for reporting, I added fix in this PR: #4994