improve task creation and cancellation

If a FrameProcessor needs to create a task it should use
FrameProcessor.create_task() and FrameProcessor.cancel_task(). This gives
Pipecat more control over all the tasks that are created in Pipecat.

Both functions internally use the utils module: utils.create_task() and
utils.cancel_task() which should also be used outside of FrameProcessors. That
is, unless strictly necessary, we should avoid using asyncio.create_task().

examples/foundational/22d-natural-conversation-gemini-audio.py

@@ -44,9 +44,7 @@ from pipecat.processors.aggregators.openai_llm_context import (
 )
 from pipecat.processors.filters.function_filter import FunctionFilter
 from pipecat.processors.frame_processor import FrameDirection, FrameProcessor
-from pipecat.processors.user_idle_processor import UserIdleProcessor
 from pipecat.services.cartesia import CartesiaTTSService
-from pipecat.services.deepgram import DeepgramSTTService
 from pipecat.services.google import GoogleLLMContext, GoogleLLMService
 from pipecat.sync.base_notifier import BaseNotifier
 from pipecat.sync.event_notifier import EventNotifier
@@ -440,11 +438,11 @@ class CompletenessCheck(FrameProcessor):
 
         if isinstance(frame, UserStartedSpeakingFrame):
             if self._idle_task:
-                self._idle_task.cancel()
+                await self.cancel_task(self._idle_task)
         elif isinstance(frame, TextFrame) and frame.text.startswith("YES"):
             logger.debug("Completeness check YES")
             if self._idle_task:
-                self._idle_task.cancel()
+                await self.cancel_task(self._idle_task)
             await self.push_frame(UserStoppedSpeakingFrame())
             await self._audio_accumulator.reset()
             await self._notifier.notify()
@@ -602,8 +600,7 @@ class OutputGate(FrameProcessor):
         self._gate_task = self.get_event_loop().create_task(self._gate_task_handler())
 
     async def _stop(self):
-        self._gate_task.cancel()
-        await self._gate_task
+        await self.cancel_task(self._gate_task)
 
     async def _gate_task_handler(self):
         while True: