Support for higher bitrates and higher fidelity audio

[tidoust]

For instance, support for multichannel audio in WebRTC.

Raised in:

• The Production Metaverse
• It's time to WHIP WebRTC into shape

[chcunningham]

Spec-wise, I think we may have the pieces we need for arbitrarily high bitrate and channel count. AudioData, AudioEncoderConfig, and AudioDecoderConfig all offer a numberOfChannels parameter. AudioEncoderConfig also has a bitrate parmater. LMK if I've overlooked anything.

Chrome-wise, we should already support 5.1 and any bitrate on decoding side. Encoding-wise, we support just opus, but I think that includes 5.1 audio (haven't tested this yet). @Djuffin fyi.