Add metric fields for Smart Suggestions in Notifications logging.

Add extra data when logging
1. whenever smart replies and actions in notifications become visible,
and
2. whenever a smart action in a notification is clicked.

Documentation:
go/ssin-metrics

Bug: 120767764
Test: tested together with ag/5764960
Change-Id: I7bc735000df9380998e0e4c8f672bca08e8707df
diff --git a/proto/src/metrics_constants/metrics_constants.proto b/proto/src/metrics_constants/metrics_constants.proto
index 66d64b1..529d78f 100644
--- a/proto/src/metrics_constants/metrics_constants.proto
+++ b/proto/src/metrics_constants/metrics_constants.proto
@@ -6649,6 +6649,21 @@
     // OS: Q
     QS_SENSOR_PRIVACY = 1598;
 
+    // Tagged data for SMART_REPLY_VISIBLE. Count of number of smart actions.
+    // OS: Q
+    NOTIFICATION_SMART_ACTION_COUNT = 1599;
+
+    // Tagged data for SMART_REPLY_VISIBLE and NOTIFICATION_ITEM_ACTION.
+    // Whether the notification has notification-assistant generated
+    // actions/replies.
+    // OS: Q
+    NOTIFICATION_SMART_SUGGESTION_ASSISTANT_GENERATED = 1600;
+
+    // Tagged data for NOTIFICATION_ITEM_ACTION. Whether the action is a smart
+    // action.
+    // OS: Q
+    NOTIFICATION_ACTION_IS_SMART = 1601;
+
     // ---- End Q Constants, all Q constants go above this line ----
 
     // Add new aosp constants above this line.