Remove AudioProcessing::ChannelLayout

This enum is no longer needed. Also moving the last piece of code from
common.h to audio_processing_impl.h, allowing to delete common.h.

Bug: chromium:1271981, b/217349489
Change-Id: If115336c36d6d7b5845a903e421c18aebfe434ee
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/251242
Reviewed-by: Sam Zackrisson <saza@webrtc.org>
Commit-Queue: Henrik Lundin <henrik.lundin@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#35946}
diff --git a/modules/audio_processing/audio_processing_impl.h b/modules/audio_processing/audio_processing_impl.h
index 32797df..47dd62e 100644
--- a/modules/audio_processing/audio_processing_impl.h
+++ b/modules/audio_processing/audio_processing_impl.h
@@ -51,6 +51,10 @@
 class ApmDataDumper;
 class AudioConverter;
 
+constexpr int RuntimeSettingQueueSize() {
+  return 100;
+}
+
 class AudioProcessingImpl : public AudioProcessing {
  public:
   // Methods forcing APM to run in a single-threaded manner.