audio: add command to purge permission cache

Add a media_audio_policy service command and helper function
in ServiceUtilities to purge permission cache.

This permists to restore the use of permission cache for
CAPTURE_AUDIO_HOTWORD permission while still  allowing CTS tests to
adopt shell permission.

Bug: 185972521
Test: atest AudioRecordSharedAudioTest
Change-Id: Ib8963053d6d7734e474174f572762abe1a4be13b
diff --git a/media/utils/include/mediautils/ServiceUtilities.h b/media/utils/include/mediautils/ServiceUtilities.h
index 9a3c6fb..6e75746 100644
--- a/media/utils/include/mediautils/ServiceUtilities.h
+++ b/media/utils/include/mediautils/ServiceUtilities.h
@@ -97,6 +97,7 @@
 bool dumpAllowed();
 bool modifyPhoneStateAllowed(const media::permission::Identity& identity);
 bool bypassInterruptionPolicyAllowed(const media::permission::Identity& identity);
+void purgePermissionCache();
 
 media::permission::Identity getCallingIdentity();