PSA: NonlinearBeamformer will be removed

[Sam Zackrisson]

Hi,

The nonlinear beamformer in the audio processing module is being deprecated, to ease refactoring and because of its very low usage.

After a week (Thursday Jun 21), I'll submit this CL which removes the API parts. CLs disabling the beamformer functionality internally and in APM will be landing in the meantime.

In summary, the following API changes will happen:

• webrtc::AudioProcessingBuilder::SetNonlinearBeamformer will be removed.
  
• webrtc::Beamforming will be removed.
  
• webrtc::ConfigOptionID::kBeamforming will be marked as deprecated.
  
• modules/audio_processing/beamformer/* will be removed.
  

[Sam Zackrisson]

Landing this now.