Refactored the comfort noise generation code in the AEC. This CL will be followed with other CLs that break apart the application of the comfort noise from the comfort noise generation.
Refactored the comfort noise generation code in the AEC.
This CL will be followed with other CLs that break apart
the application of the comfort noise from the comfort
noise generation.

The changes in the CL are very close to bitexaxt. The
bitinexactness is caused by differences in numerical
behavior when bundling the spectral band power and the
noise scaling based on the NLP gain.

BUG=webrtc:5201, webrtc:5298

Review-Url: https://codereview.webrtc.org/1958933002
Cr-Original-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#12713}
Cr-Mirrored-From: https://chromium.googlesource.com/external/webrtc
Cr-Mirrored-Commit: 5df729489f4c27e6325f08671dc5bf10d8c14a31

Alkalyne/webrtctrunk,Alkalyne/webrtctrunk,jchavanton/webrtc,Alkalyne/webrtctrunk,jchavanton/webrtc,Alkalyne/webrtctrunk,Alkalyne/webrtctrunk,jchavanton/webrtc,Alkalyne/webrtctrunk,jchavanton/webrtc,Alkalyne/webrtctrunk,jchavanton/webrtc,jchavanton/webrtc,Alkalyne/webrtctrunk,jchavanton/webrtc