feat: support new async-tool mechanism in AWS Nova Sonic

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.

examples/realtime/realtime-aws-nova-sonic.py

@@ -5,7 +5,6 @@
 #
 
 
-import asyncio
 import os
 import random
 from datetime import datetime
@@ -46,11 +45,6 @@ async def fetch_weather_from_api(params: FunctionCallParams):
         if params.arguments["format"] == "fahrenheit"
         else random.randint(15, 30)
     )
-    # Simulate a long network delay.
-    # You can continue chatting while waiting for this to complete.
-    # With Nova 2 Sonic (the default model), the assistant will respond
-    # appropriately once the function call is complete.
-    await asyncio.sleep(5)
     await params.result_callback(
         {
             "conditions": "nice",
@@ -150,9 +144,7 @@ async def run_bot(transport: BaseTransport, runner_args: RunnerArguments):
     # Register function for function calls
     # you can either register a single function for all function calls, or specific functions
     # llm.register_function(None, fetch_weather_from_api)
-    llm.register_function(
-        "get_current_weather", fetch_weather_from_api, cancel_on_interruption=False
-    )
+    llm.register_function("get_current_weather", fetch_weather_from_api)
 
     # Set up context and context management.
     context = LLMContext(tools=tools)