Internal refactoring of AGC2. This CL is needed in preparation for its child CL to correctly show the upcoming changes in the diff. Bug: webrtc:7494 Change-Id: If7f837e064243d5ffe09e21fc68f489bb00dfdc5 Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/234527 Reviewed-by: Hanna Silen <silen@webrtc.org> Commit-Queue: Alessio Bazzica <alessiob@webrtc.org> Cr-Commit-Position: refs/heads/main@{#35170}