Move smoothing filter to common audio and exp_filter to base/analytics.

An earlier attempt of this work can be found here https://codereview.webrtc.org/2520003005/#ps100001, but was reverted.

PS4 in that CL was not valid since separation of BUILD.gn can cause internal bot to fail.

This is a new attempt, which is the same as https://codereview.webrtc.org/2520003005/#ps100001 but PS4 reverted.

BUG=webrtc:6443
TBR=tommi@webrtc.org, solenberg@webrtc.org

Review-Url: https://codereview.webrtc.org/2532523002
Cr-Commit-Position: refs/heads/master@{#15233}
diff --git a/webrtc/modules/video_coding/media_opt_util.h b/webrtc/modules/video_coding/media_opt_util.h
index 26f9332..bab1cbe 100644
--- a/webrtc/modules/video_coding/media_opt_util.h
+++ b/webrtc/modules/video_coding/media_opt_util.h
@@ -16,7 +16,7 @@
 
 #include <memory>
 
-#include "webrtc/base/exp_filter.h"
+#include "webrtc/base/analytics/exp_filter.h"
 #include "webrtc/modules/video_coding/internal_defines.h"
 #include "webrtc/system_wrappers/include/trace.h"
 #include "webrtc/typedefs.h"