Added tools and tool_resources to Assistant and ThreadRequest structures

[zmagdum]

Assistants have changed in V2 version need to adjust accordingly. Link for docs is below

We are migrating assistants from v1 to v2 and have files associated with them. When we switched OpenAI was returning error saying there are no files associated with the assistant. V2 version takes to files little differently

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Describe the change
The change add Tools and ToolResources to ThreadRequest structure and ToolResources to Assistant structure. With this when you retrieve assistant you get tool resource and you can pass that along when you create a thread. Without this you can not create threads and OpenAI returns error saying tool_resources.code_interpreter.file_ids is required

Provide OpenAI documentation link
https://platform.openai.com/docs/assistants/migration

Describe your solution
Solution is simple to update the response definitions for v2 version of the assistant. .

Tests
Did not add any tests. Ran current tests and they seem to be working fine

Additional context
Here is how we use it.

	config := openai.DefaultConfig(token)
	config.AssistantVersion = "v2"
	client := openai.NewClientWithConfig(config)
	assistant, err := client.RetrieveAssistant(ctx, assistantName)
	if err != nil {
		return result, err
	}
	log.Printf("found assistant: %v", assistant)
        thread, err := client.CreateThread(ctx, openai.ThreadRequest{ToolResources: assistant.ToolResources})
        if err != nil {
                return result, err
        }

Issue: #XXXX