audio policy: add recording app ops monitoring for system services

Allow audio recording app ops monitoring for system services.
Only audioserver UID and shell should be exempt from being silenced by
app ops.

Bug: 192638296
Test: run app that records audio, then $adb shell appops set <UID> 27 2
Test: atest GtsSuspendAppsTestCases:SuspendPackagesTest
Change-Id: Ibbe79add05e8f31175c2db7d43fe48af4ebd9d29