Move the check for analog gain changes so that it can be used independently of echo_controller. This change is needed to land https://webrtc-review.googlesource.com/c/src/+/234140. Bug: webrtc:12774 Change-Id: I9ea127b0a4d374f31493d6f8afcacee40fa9257c Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/234383 Commit-Queue: Hanna Silen <silen@webrtc.org> Reviewed-by: Alessio Bazzica <alessiob@webrtc.org> Cr-Commit-Position: refs/heads/main@{#35159}