Reland "Deprecate the adaptive level controller"

This is a reland of 6f37ed78d99daa36e964ff0a65b205f0916d9949

CQ dry run OK except for missing iOS swarming bots.
NOTRY=True

Original change's description:
> Deprecate the adaptive level controller
>
> Level control handled by default-on AGC.
>
> Bug: none
> Change-Id: I405daeceece12c896d41156b649fcfd556726f77
> Reviewed-on: https://webrtc-review.googlesource.com/59682
> Reviewed-by: Fredrik Solenberg <solenberg@webrtc.org>
> Reviewed-by: Alex Loiko <aleloi@webrtc.org>
> Commit-Queue: Sam Zackrisson <saza@webrtc.org>
> Cr-Commit-Position: refs/heads/master@{#22305}

Bug: none
Change-Id: I0b9b8e2f3457d5efd4603efbfbbc6b84651df315
Reviewed-on: https://webrtc-review.googlesource.com/60720
Commit-Queue: Sam Zackrisson <saza@webrtc.org>
Reviewed-by: Fredrik Solenberg <solenberg@webrtc.org>
Reviewed-by: Alex Loiko <aleloi@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#22352}
diff --git a/modules/audio_processing/include/config.h b/modules/audio_processing/include/config.h
index 7c34de8..7615f62 100644
--- a/modules/audio_processing/include/config.h
+++ b/modules/audio_processing/include/config.h
@@ -35,7 +35,7 @@
   kIntelligibility,
   kEchoCanceller3,  // Deprecated
   kAecRefinedAdaptiveFilter,
-  kLevelControl
+  kLevelControl  // Deprecated
 };
 
 // Class Config is designed to ease passing a set of options across webrtc code.