Add support to AWSNovaSonicLLMService for the new "async tool call"
mechanism activated by `cancel_on_interruption=False`, which includes:
- delivering results asynchronously
- delivering result streams
- cancelling running async tools
Note that the introduction of the new mechanism had actually caused a
regression in AWS Nova Sonic, which previously supported
`cancel_on_interruption=False` with the old mechanism (simply avoiding
discarding tool calls on interruptions).
Support for the other major realtime services (`GeminiLiveLLMService`,
`OpenAIRealtimeLLMService`) will follow in a separate PR — Gemini Live
in particular needs more work before it can support long-running tool
calls reliably.
7d3726a74b