Add ToolChoice to CreateRunRequest class

[marcusx2]

Feature Request

Is your feature request related to a problem? Please describe.

With the new version of OpenAPI, the tool can be ignored and not used if the tool choice is left with its default value.

Describe the solution you'd like

Add a new property to the CreateRunRequest method, as such

[Preserve]
[JsonProperty("tool_choice")]
public IReadOnlyDictionary<string, string> ToolChoice { get; }