Add unaudited exported flag to exposed runtime receivers

Android T allows apps to declare a runtime receiver as not exported
by invoking registerReceiver with a new RECEIVER_NOT_EXPORTED flag;
receivers registered with this flag will only receive broadcasts from
the platform and the app itself. However to ensure developers can
properly protect their receivers, all apps targeting U or later
registering a receiver for non-system broadcasts must specify either
the exported or not exported flag when invoking #registerReceiver;
if one of these flags is not provided, the platform will throw a
SecurityException. This commit updates all the exposed receivers
with a new RECEIVER_EXPORTED_UNAUDITED flag to maintain the existing
behavior of exporting the receiver while also flagging the receiver
for audit before the U release.

Bug: 234659204
Test: Build
Change-Id: Id0561bcf873eb22cce7bd80fa2600740d9fbd40d

services/core/java/com/android/server/display/BrightnessTracker.java

@@ -1133,7 +1133,7 @@ public class BrightnessTracker {
 
         public void registerReceiver(Context context,
                 BroadcastReceiver receiver, IntentFilter filter) {
-            context.registerReceiver(receiver, filter);
+            context.registerReceiver(receiver, filter, Context.RECEIVER_EXPORTED_UNAUDITED);
         }
 
         public void unregisterReceiver(Context context,