Add notification ID for APM enhancement

Bug: 239983569
Test: atest com.android.server.wifi
Change-Id: I1cb0ec847040e47b563b39b622e12c49e41082bc

proto/src/system_messages.proto

@@ -298,6 +298,10 @@ message SystemMessage {
     // Notify the user to setup their dock
     NOTE_SETUP_DOCK = 72;
 
+    // Inform the user of wifi apm state changes.
+    // Package: android
+    NOTE_WIFI_APM_NOTIFICATION = 73;
+
     // ADD_NEW_IDS_ABOVE_THIS_LINE
     // Legacy IDs with arbitrary values appear below
     // Legacy IDs existed as stable non-conflicting constants prior to the O release