[FR] file AOSP feature requests for the additional hidden API usage introduced since the last round

[nift4]

1. volume listener (1. broadcast or settings content observer is also hidden/improper API but its not even sufficient, because it has at least 500ms delay 2. the api I'm using atm is even more hidden, but at least has no delay), https://github.com/FoedusProgramme/Gramophone/blob/9e035255be850f60d2478e94601056024fdab0ea/misc/audiofxfwd/src/main/java/org/nift4/audiofxfwd/VolumeGroupCallbackAdapter.java and https://github.com/FoedusProgramme/Gramophone/blob/9e035255be850f60d2478e94601056024fdab0ea/hificore/src/main/java/org/nift4/audiosysfwd/AudioVolumeGroupCallbackAdapter.java
2. dpe canary via ReflectionAudioEffect, because DPE doesn't support control listener (ie you have low priority) as it just crashes you if you try to init it without having control. also, can do the "it doesn't release() when init fails" bug as well.
3. check if effect offloadable api
4. get effect config for displaying
5. detect A2DP offload yes/no for displaying
6. detect device volume behavior (a2dp, hdmi, all of them) absolute or not so that I know whether or not I have any headroom (there was old report closed with "i don't get why you need it")
7. detect why offload is not working (replacement for getMasterMono)
8. maybe getMasterVolume, getMasterMono for headroom calculation (or does getStreamVolumeDb take these into account?)