Enable the voice_activation_permission_apis flag control, replace the static boolean control.

When flags are set as default: false
1) no voice activation op noted:https://paste.googleplex.com/5323105500135424
Privacy dashboard: https://screenshot.googleplex.com/4kpXpp2tbsdRuhh

When set flags : true
I. Enable voice activation op to be noted:
i) adb shell device_config put permissions android.permission.flags.voice_activation_permission_apis true
ii) Trigger the Assisstant app by i.e. "OK Google...".
iii) adb shell dumpsys appops --package com.google.android.googlequicksearchbox
Should see the voice activation op "RECEIVE_SANDBOX_TRIGGER_AUDIO" noted.
sample output:
https://paste.googleplex.com/6143516865462272

Bug: 289087412
Change-Id: Ib29972c59e8a1305860a3c8d326d957b50cc0b5a
Test: presubmit