Remove no-op and unused methods from AudioCodingModule

This CL removes the following no-op and/or unused methods from
AudioCodingModule and AudioCodingModuleImpl:

ConfigISACBandwidthEstimator
DecoderEstimatedBandwidth
IsInternalDTXReplacedWithWebRtc
REDPayloadISAC
ReplaceInternalDTXWithWebRtc
ResetDecoder
ResetEncoder
SendBitrate
SetReceivedEstimatedBandwidth

R=henrik.lundin@webrtc.org

Review URL: https://codereview.webrtc.org/1308283003 .

Cr-Commit-Position: refs/heads/master@{#9773}
8 files changed