Allows implementers to register callback methods that will be executed when a
CacheManager event occurs.
The lifecycle events are:
init
dispose
CacheManager change events are:
adding a Cache
removing a Cache
Note that the caches that are part of the initial configuration are not considered "changes".
It is only caches added or removed beyond the initial config.
Callbacks to these methods are synchronous and unsynchronized.
Registered listeners for registering and unregistering CacheManagerEventListeners and sending notifications to registrants.
There is one of these per CacheManager.