AGC2: max output noise level now part of config

Tested: bit-exactness verified with audioproc_f

Bug: webrtc:7494
Change-Id: Ic42f09dc13560494963cdcd338a0c52a729e108d
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/186266
Commit-Queue: Alessio Bazzica <alessiob@webrtc.org>
Reviewed-by: Jakob Ivarsson <jakobi@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#32282}

modules/audio_processing/include/audio_processing.h

@@ -354,6 +354,7 @@ class RTC_EXPORT AudioProcessing : public rtc::RefCountInterface {
         float extra_saturation_margin_db = 2.f;
         int gain_applier_adjacent_speech_frames_threshold = 1;
         float max_gain_change_db_per_second = 3.f;
+        float max_output_noise_level_dbfs = -50.f;
       } adaptive_digital;
     } gain_controller2;