Generalized the hysteresis behavior in the AEC3 delay estimator

This CL generalizes the hysteresis behavior on the AEC3 delay estimator
to be two-sided and easier to configure.


Bug: webrtc:8671
Change-Id: Ife21c1511416e32eb3618c81178deefe332ac1e8
Reviewed-on: https://webrtc-review.googlesource.com/39267
Reviewed-by: Gustaf Ullberg <gustaf@webrtc.org>
Commit-Queue: Per Åhgren <peah@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#21604}

modules/audio_processing/include/audio_processing.h

@@ -1238,6 +1238,9 @@ struct EchoCanceller3Config {
     size_t num_filters = 4;
     size_t api_call_jitter_blocks = 26;
     size_t min_echo_path_delay_blocks = 5;
+    size_t delay_headroom_blocks = 1;
+    size_t hysteresis_limit_1_blocks = 1;
+    size_t hysteresis_limit_2_blocks = 0;
   } delay;
 
   struct Filter {