Stop using the beamformer inside APM

Removes the usage of an injected/enabled beamformer in APM, and marks
the API parts as deprecated.
Initialization and process calls are removed, and all enabled/disabled
flags are replaced by assuming no beamforming. Additionally, an AGC test
relying on the beamformer as a VAD is removed.

Bug: webrtc:9402
Change-Id: I0d3d0b9773da083ce43c28045db9a77278f59f95
Reviewed-on: https://webrtc-review.googlesource.com/83341
Reviewed-by: Minyue Li <minyue@webrtc.org>
Commit-Queue: Sam Zackrisson <saza@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#23643}
diff --git a/modules/audio_processing/include/config.h b/modules/audio_processing/include/config.h
index 338fcea..4e318c9 100644
--- a/modules/audio_processing/include/config.h
+++ b/modules/audio_processing/include/config.h
@@ -30,7 +30,7 @@
   kDelayAgnostic,
   kExperimentalAgc,
   kExperimentalNs,
-  kBeamforming,
+  kBeamforming,  // Deprecated
   kIntelligibility,
   kEchoCanceller3,  // Deprecated
   kAecRefinedAdaptiveFilter,