[non-BE] Merging dlb/cont-47-low-bitrate-SBA-update2 into main

These changes harmonise SBA operation at 13.2kbps and 16.4kbps, within the SPAR-DirAC framework. Also included is adaptive smoothing for HOA2 and HOA3 outputs, and bitrate switching cleanup.

Non-BE modes expected are 13.2kbps and 16.4kbps.