Add ChronicleHash.offHeapMemoryUsed() method; Centralized management of all direct memory and file resources of ChronicleMap in one Cleaner

src/main/java/net/openhft/chronicle/set/SetFromMap.java

@@ -116,6 +116,11 @@ class SetFromMap<E> extends AbstractSet<E> implements ChronicleSet<E> {
         return m.longSize();
     }
 
+    @Override
+    public long offHeapMemoryUsed() {
+        return m.offHeapMemoryUsed();
+    }
+
     @Override
     public Class<E> keyClass() {
         return m.keyClass();