Changes to implicit signalling for AAC introduced bugs  599846  and  599625 .

The fixes for those bugs involve failing if we receive an unsupported config change midstream. Currently, we treat those failures as PIPELINE_ERROR_DECODE.

As per DaleCurtis' suggestion, we should add an AUDIO_RENDER_ERROR_IMPLICIT_CONFIG_CHANGE error and track it properly, in order to have better failure metrics.