.NET: Investigate adding abstractions to retrieve generated code

At the moment we need to break glass to extract the code generated by the code interpreter tool. The purpose of this task is to investigate to see can abstractions be introduced to handle this.

```csharp
// Extract the code generated by code interpreter tool
var chatResponse = response.RawRepresentation as ChatResponse;
StringBuilder generatedCode = new();
foreach (object? updateRawRepresentation in chatResponse?.RawRepresentation as IEnumerable ?? [])
{
if (updateRawRepresentation is RunStepDetailsUpdate update && update.CodeInterpreterInput is not null)
{
generatedCode.Append(update.CodeInterpreterInput);
}
}
Console.WriteLine($"\nGenerated Code:\n{generatedCode}");
```

Start with the C# extraction example and inspect ChatResponse, RunStepDetailsUpdate, and CodeInterpreterInput to understand how generated code is currently exposed. The investigation is complete when a suitable abstraction for retrieving generated code is defined and its scope is documented.

Written by the indexing model from the issue text.