Post notification on abusive background current drain

Tapping on the notification will bring up the individual abusive
app's battery settings page. It won't be re-posted after being
dismissed until next day, in order to avoid from spamming the user.

Bug: 200326767
Bug: 203105544
Test: FrameworksMockingServicesTests:BackgroundRestrictionTest
Test: Manual - adb shell am set-bg-abusive-uids & verify notification
Change-Id: I0b30014d748863c66c3845b5f310948a9493e302
diff --git a/proto/src/system_messages.proto b/proto/src/system_messages.proto
index 196c6aa..e89dda9 100644
--- a/proto/src/system_messages.proto
+++ b/proto/src/system_messages.proto
@@ -362,5 +362,11 @@
     // Notify the user that some accessibility service has view and control permissions.
     // package: android
     NOTE_A11Y_VIEW_AND_CONTROL_ACCESS = 1005;
+
+    // Notify the user an abusive background app has been detected.
+    // Package: android
+    // Note: this is a base ID, multiple notifications will be posted for each
+    // abusive apps, with notification ID based off this ID.
+    NOTE_ABUSIVE_BG_APPS_BASE = 0xc1b2508; // 203105544
   }
 }