Add summary stats for CP services (#1180)

docs/modules/ROOT/pages/list-of-metrics.adoc

@@ -1369,6 +1369,24 @@ This is because the cluster has to communicate with more members, which can add
 |count
 |Version number of the CP session, basically it shows how many times the session heartbeat is received
 |===
+
+We also have per-object type a `summary` section which provides live and destroyed object counts grouped by CP Group. These can be found under `cp.{atomiclong,atomicref,countdownlatch,lock,map,semaphore}.summary` and provide the following child attributes.
+
+[cols="4,1,6a"]
+|===
+| Name
+| Unit
+| Description
+
+|`destroyed.count`
+|count
+|Number of objects for the parent object type that have been destroyed. Also referred to as the tombstoned object count.
+
+|`live.count`
+|count
+|Number of objects for the parent object type that are in use.
+|===
+
 ====
 
 .Events