Audio flags: add flag for AAOS protection of volume API

Add flag auto_public_volume_api_hardening
in package com.android.media.audio.flags for the
hardening of volume APIs in android.media.AudioManager
for automotive use cases.

Bug: 302751899
Test: atest android.media.audio.cts.AudioManagerTest
Change-Id: I5629be93dba8e35ff0d557c11524f584a2552805