Technical Debt: Complete Audio Channel support in AudionCaptureSrc and FrameType AUDIO

[kumaakh]

1. Typical audio metadata should include sampling rate, number of channels and bitdepth. Currently we assume single channel signed 16bit inetegers with unknown sampling rate, this should be fixed by defining AudioFrameMetadata and use it every where.
2. The initial implementation of Audio Capture Src has number of channels as a property but the ouput frame metadata does not support channels. It is not clear how the system will behave if a stereo capture is performed via this source.
3. Likweise 24 bit and 32 bit audio (HD) are fairly popular now. hene we should pay this deby quickly.
4. This issue should also make sure that all downstream modules are fixed to use channels and bitdepth rather than assuming