Microphone and mWW Improvements

[kahrendt]

• Reading from I2S microphone is in a task
  • Handles the hacked 48kHz audio that triplicates the 16kHz signal in the current 48kHz XMOS firmware
  • Puts left and right channels into separate ring buffers to pass less filtered audio to mWW and the fully clean file to the voice assistant (prepared for a future XMOS firmware update)
  • TODO: These changes really should be under a new microphone platform, not bolted onto the existing I2S microphone
• mWW runs in tasks instead of in the main loop: one for spectrogram feature generation and another for the actual inference
  • Tasks communicate and are controlled by an Event Group
  • Wake word detection information is passed from the inference task to the main loop using a queue
• mWW models can be enabled or disabled on the fly. They will automatically be loaded and unloaded as needed
• mWW will always run unless stopped, even while the assist pipeline is running

I'm holding off merging because I haven't tested it on the 16 kHz XMOS firmware that most people are running. I may have broken the microphone!

This will require a follow up PR after merging to change the external component branch back to dev in the yaml file