8248401: Refactor/unify RMI gc support functionality

Move recent timestamp of most recent whole heap liveness analysis into CollectedHeap, removing the duplicates in all collectors

Reviewed-by: kbarrett, ayang, stefank

src/hotspot/share/gc/shenandoah/shenandoahControlThread.cpp

@@ -235,6 +235,9 @@ void ShenandoahControlThread::run_service() {
         // global soft refs policy, and we better report it every time heap
         // usage goes down.
         Universe::update_heap_info_at_gc();
+
+        // Signal that we have completed a visit to all live objects.
+        Universe::heap()->record_whole_heap_examined_timestamp();
       }
 
       // Disable forced counters update, and update counters one more time