Better notification to user when DNS-over-TLS is broken

Provide a specifc notification to let users know that device
has no internet is because it really doesn't have internet access
or it's caused by private DNS resolution failed.

Bug: 113242081
Test: atest FrameworksNetTests
Change-Id: I710c88a4742f5fd56c39fc797d7fa3ad36dba553
diff --git a/proto/src/system_messages.proto b/proto/src/system_messages.proto
index ffbf1ae..ef071a4 100644
--- a/proto/src/system_messages.proto
+++ b/proto/src/system_messages.proto
@@ -249,6 +249,8 @@
     NOTE_NETWORK_LOGGED_IN = 744;
     // A partial connectivity network was detected during network validation
     NOTE_NETWORK_PARTIAL_CONNECTIVITY = 745;
+    // Private DNS is broken in strict mode
+    NOTE_NETWORK_PRIVATE_DNS_BROKEN = 746;
 
     // Notify the user that their work profile has been deleted
     // Package: android