fix(migration): speed up step 11 (#6086)

cmd/setup/11/11_update_events.sql

@@ -0,0 +1,21 @@
+UPDATE eventstore.events SET 
+    created_at =  creation_date 
+FROM (
+    SELECT 
+        e.event_sequence as seq
+        , e.instance_id as i_id
+        , e.creation_date as cd
+    FROM 
+        eventstore.events e
+    WHERE 
+        created_at IS NULL
+    ORDER BY 
+        event_sequence ASC
+        , instance_id 
+    LIMIT $1
+) AS e 
+WHERE 
+    e.seq = eventstore.events.event_sequence 
+    AND e.i_id = eventstore.events.instance_id 
+    AND e.cd = eventstore.events.creation_date
+;