Internal refactoring of AGC2 to decouple the VAD, its wrapper and the peak and RMS level measurements. Bit exactness verified with audioproc_f on a collection of AEC dumps and Wav files (42 recordings in total). Bug: webrtc:7494 Change-Id: Ib560f1fcaa601557f4f30e47025c69e91b1b62e0 Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/234524 Commit-Queue: Alessio Bazzica <alessiob@webrtc.org> Reviewed-by: Hanna Silen <silen@webrtc.org> Cr-Commit-Position: refs/heads/main@{#35208}