Revert "APM: rename AnalogGainStatsReporter to InputVolumeStatsReporter"

This reverts commit b5319fabeeda4ffbf58f28f4ee3d5c7c3868fb3b.

Reason for revert: audioproc_f crash 

Original change's description:
> APM: rename `AnalogGainStatsReporter` to `InputVolumeStatsReporter`
>
> Adopt the new naming convention, which replaces "analog gain" and
> "mic level" with "input volume", in the input volume stats reporter.
>
> Bug: webrtc:7494
> Change-Id: Ia24876151f51dd1dcc4e4f9db56c64d11ae3b442
> Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/279840
> Reviewed-by: Hanna Silen <silen@webrtc.org>
> Commit-Queue: Alessio Bazzica <alessiob@webrtc.org>
> Cr-Commit-Position: refs/heads/main@{#38467}

Bug: webrtc:7494
Change-Id: Ia943a57c93fc77eb8450fab17961e60774e10f02
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/280600
Bot-Commit: rubber-stamper@appspot.gserviceaccount.com <rubber-stamper@appspot.gserviceaccount.com>
Commit-Queue: Alessio Bazzica <alessiob@webrtc.org>
Auto-Submit: Alessio Bazzica <alessiob@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#38478}

modules/audio_processing/audio_processing_impl.cc

@@ -1131,7 +1131,8 @@ int AudioProcessingImpl::ProcessCaptureStreamLocked() {
   }
 
   if (capture_.applied_input_volume.has_value()) {
-    applied_input_volume_stats_reporter_.UpdateStatistics(
+    // Log the applied input volume only when available.
+    input_volume_stats_reporter_.UpdateStatistics(
         *capture_.applied_input_volume);
   }