AudioStreamConverter

[Mysticial]

Adds 3 new audio processing modules:

• AudioStreamConverter: Takes a raw audio stream and converts to/from the float format. (this is a newer version of AudioStreamConversion with more SIMD)
• AudioChannelInterleave: Takes a stream of audio frames (interleaved channels) and splits them into separate single-channel streams. Also does the reverse direction.
• AudioChannelMixer: Takes an N-channel audio stream and converts it to an M-channel stream using a custom weight matrix.

Thus our future audio pipeline will be:

1. Receive an arbitrary audio stream from the capture card.
2. If it's not already float we convert it to float using AudioStreamConverter.
3. If it's multiple channels, we deinterleave it into separate streams using AudioChannelInterleave.

For the audio playback path:
4. If the sample rate does not match the audio sink's sample rate, resample it using AudioResampler.
5. Re-interleave the channels using AudioChannelInterleave.
6. Convert to the audio sink's desired format using AudioStreamConverter.

For the FFT/inference path:
4. If the sample rate is not 48 kHz, we resample it to 48 kHz using AudioResampler.
5. We collapse the streams into 1 channel using AudioChannelMixer.
6. Perform FFTs and inference.

Step 4 on both branches may be optimized to one step if the conversion is identical.