MediaRecorder: add privileged permission for AudioSource.RADIO_TUNER

MediaRecorder.AudioSource.RADIO_TUNER is @SystemApi and as such
must be guarded by a privileged permission.
Use android.permission.CAPTURE_AUDIO_OUTPUT as it matches the
use case of capturing what is played by the device and not
capturing from a microphone.

Bug: 135717621
Test: CTS tests for AudioRecord
Change-Id: Ic5dc191cb2340d7614f51c5acb0bac6156d214ab