Add IAudioManager methods for tracking client recording activity

audio_unique_id_t IAudioManager::trackRecorder(IBinder token)
  - registers a client recorder withing Audio Service,
    returns a unique tracking recording ID (RIID);
    Audio Service tracks the lifetime of the recorder using
    the provided token.

oneway recorderEvent(int riid, int event)
  - updates the current state of the client;
    only "started" and "stoped" states are considered.

Bug: 123312504
Test: android.media.cts.AudioRecordingConfigurationTest
      AudioRecordTest#testAudioRecordInfoCallback
      MediaRecorderTest#testAudioRecordInfoCallback
      manual testing using Oboe and Solo test apps

Change-Id: Iddb1b91fff7127ab35ba1d33e3e6c32937ac3081