[MTE] show notification if using MTE bootloader switch.

ro.arm64.memtag.bootctl_supported can be set by OEMs that do not want to
enable MTE by default yet but want to offer users a preview that can be
enabled in the Developer Options. This developer option will reboot the
phone and enable MTE. In that case we want to show a notification to
make sure the user does not forget that it is enabled.

Bug: 206895651
Change-Id: Iaebc16d4b8d0da302f18709e23062f4a5bd58fe3
diff --git a/proto/src/system_messages.proto b/proto/src/system_messages.proto
index 196c6aa..3648593 100644
--- a/proto/src/system_messages.proto
+++ b/proto/src/system_messages.proto
@@ -282,6 +282,10 @@
     // Notify the user to set up dream
     NOTE_SETUP_DREAM = 68;
 
+    // Inform the user that MTE override is active.
+    // Package: android
+    NOTE_MTE_OVERRIDE_ENABLED = 69;
+
     // 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