ISPN-4979 CacheStatusResponse map uses too much memory

* Added in way to cache various instances in the serialization context

https://issues.jboss.org/browse/ISPN-4979
In the ISPN-3561 fix I introduced a `ManagerStatusResponse` class to contain all the cache statuses from one node. I wonder if we could make that extend `InstanceReusingAdvancedExternalizer` and make `MapExternalizer` a regular externalizer?