Add DS->SQL replay cron job to production

This won't do anything until we set the migration schedule to
DATASTORE_PRIMARY. Actions in order:

1. Add this cron job (it'll be a no-op)
2. Run the init-sql-pipeline to populate production's SQL DB
3. Set the SqlReplayCheckpoint to a time before the smear backup that
was used in step #1 (maybe 30 minutes)
4. Set the database migration schedule to transition to
DATASTORE_PRIMARY at some point

Author: gbrodman

core/src/main/java/google/registry/env/production/default/WEB-INF/cron.xml

@@ -330,4 +330,13 @@
     <schedule>every day 15:00</schedule>
     <target>backend</target>
   </cron>
+
+  <cron>
+    <url><![CDATA[/_dr/cron/fanout?queue=replay-commit-logs-to-sql&endpoint=/_dr/task/replayCommitLogsToSql&runInEmpty]]></url>
+    <description>
+      Replays recent commit logs from Datastore to the SQL secondary backend.
+    </description>
+    <schedule>every 3 minutes</schedule>
+    <target>backend</target>
+  </cron>
 </cronentries>