AGC2 limiter stats + config ToString missing param

Bug: webrtc:7494
Change-Id: Icb6a164882af5c15c9400eb869dccbfda20b3da7
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/194324
Commit-Queue: Alessio Bazzica <alessiob@webrtc.org>
Reviewed-by: Jakob Ivarsson <jakobi@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#32653}

modules/audio_processing/gain_controller2.h

@@ -46,6 +46,7 @@ class GainController2 {
   GainApplier gain_applier_;
   std::unique_ptr<AdaptiveAgc> adaptive_agc_;
   Limiter limiter_;
+  int calls_since_last_limiter_log_;
   int analog_level_ = -1;
 
   RTC_DISALLOW_COPY_AND_ASSIGN(GainController2);