Make the separation between target and interferer scenario depend on microphone spacing in NonlinearBeamformer

Depends on this CL: https://codereview.webrtc.org/1378973003/

Review URL: https://codereview.webrtc.org/1388033002

Cr-Original-Commit-Position: refs/heads/master@{#10330}
Cr-Mirrored-From: https://chromium.googlesource.com/external/webrtc
Cr-Mirrored-Commit: 4a66e4a4d8847cef1e61aec6978f64dddece3d96
8 files changed