support ChannelMappingAudioProcessor in float output mode

[nift4]

[REQUIRED] Use case description

It appears like ChannelMappingAudioProcessor is required for compliant playback of Vorbis and Opus files that use more than two channels on most devices (ref b1541b0). In float output mode, ChannelMappingAudioProcessor is silently skipped, causing playback to use wrong chanel order.

Proposed solution

Implement ChannelMappingAudioProcessor in float output mode.

Alternatives considered

N/A