Implement tool_calls handling for chat completions streaming pipeline

[declark1]

For chat completions streaming, tool_calls is not currently being set for the chat completion chunk choice in output_detection_response() as the logic to merge tool call chunks has not yet been implemented.

merge_tool_calls() is being added with #498, which can be leveraged here, however, this needs further investigation and testing and additional logic may be required to properly build tool_calls for batches.