We now distinguish between input and output audio and image frames. We introduce
`InputAudioRawFrame`, `OutputAudioRawFrame`, `InputImageRawFrame` and
`OutputImageRawFrame` (and other subclasses of those). The input frames usually
come from an input transport and are meant to be processed inside the pipeline
to generate new frames. However, the input frames will not be sent through an
output transport. The output frames can also be processed by any frame processor
in the pipeline and they are allowed to be sent by the output transport.
created twilio_websocket_service.py, TwilioFrameSerializer.py
moved pcm_16000_to_ulaw_8000 and ulaw_8000_to_pcm_16000 to src/pipecat/utils/audio.py
fixed callback on disconnect
