Add explicit private audio recording request

Add the possibility for apps to indicate that their
capture use case is private and that a privileged Assistant
should not be able to capture concurrently.
This allows to override the default behavior tied to the audio
source (e.g VOICE_COMMUNICATION is private by default but
UNPROCESSED is not).

- Add AAudio API to set and get privacy sensitive mode on input stream
- Add MediaRecorder API to set and get privacy sensitive mode
- Modify AudioSource constructor to accept audio attributes instead of an
audio source to specify the use case.
- Modify audio policy concurrent capture logic to use audio attributes
flag instead of audio source to decide of a capture client has
requested privacy mode or not.

Bug: 137850106
Test: CTS AudioRecordTest and MediaRecorderTest, manual audio smoke tests

Change-Id: I250ea5da4c1da809ceac0da22ae9bee15b937001