GEODE-7483: Add Generational ZGC (#7896)

Author: henri-tremblay

geode-core/src/main/java/org/apache/geode/internal/cache/control/HeapMemoryMonitor.java

@@ -175,6 +175,7 @@ static boolean isTenured(MemoryPoolMXBean memoryPoolMXBean) {
         || name.equals("Tenured Gen") // Hitachi 1.5 GC
         || name.equals("Java heap") // IBM 1.5, 1.6 GC
         || name.equals("GenPauseless Old Gen") // azul C4/GPGC collector
+        || name.equals("ZGC Old Generation") // Generational ZGC
         || name.equals("ZHeap") // ZGC
 
         // Allow an unknown pool name to monitor