This CL refactors the delay estimator in AEC3. Furthermore, it adds: 1. Allow for a customized delay estimator behavior to simplify development. 2. Exposes that behavior to clear configuration settings. 3. Adds logging of the delay range supported by the delay estimator. Bug: webrtc:8519 Change-Id: I1764a090519a78b021b2e7de565c52a6c02c848e Reviewed-on: https://webrtc-review.googlesource.com/21166 Commit-Queue: Per Åhgren <peah@webrtc.org> Reviewed-by: Gustaf Ullberg <gustaf@webrtc.org> Cr-Commit-Position: refs/heads/master@{#20733}