MB-11553 Reduce the min/default/max number of checkpoint items.

As UPR can efficiently avoid the full re-materialization in
replication, we should reduce the min/default/max number of items
maintained per checkpoint, which were determined before based on
TAP-based replication.

Change-Id: If57ea1c2ca66b9c7e8a76a99767a66af49db0d9b
Reviewed-on: http://review.couchbase.org/39040
Reviewed-by: abhinav dangeti <abhinav@couchbase.com>
Tested-by: abhinav dangeti <abhinav@couchbase.com>