Audio: add system API AudioManager.isScoManagedByAudio()

The API indicates if both the feature flag and the system property
controlling the new SCO audio activation mode controlled by the audio
framework are enabled.

Bug: 265057196
Test: atest AudioManagerTest#testIsScoManagedByAudio
Flag: android.media.audio.sco_managed_by_audio
Change-Id: If823ae7b9cbf81cdf8429d046839f7c5f7ec84e2