OPENDJ-1231 Make the Medium Consistency Point support replica heartbeats


Code cleanup: removed code that has been obsoleted by having the separate ChangeNumberIndexer thread.
Matt and I think that this code was necessary because the change number was computed lazily.
Now that the change number is computed eagerly, there is no need for this obsolete code.


Additional potential work that might be done later:
- Could we remove the counter records from the replicaDBs?
- Could we remove ECLServerHandler.eligibleCSN()?


ReplicationServer.java:
In getECLChangeNumberLimits():
- removed the for loop inferring the "eligibleCount", i.e. the number of changes that are in the replicaDBs but not yet in the ChangeNumberIndexDB
- removed all the parameters which are now useless

ReplicationServerDomain.java, ReplicationDomainDB.java, JEChangelogDB.java, JEReplicaDB.java, ReplicationDB.java:
Transitively removed all the methods that were called by ReplicationServer.getECLChangeNumberLimits().

ECLServerHandler.java, FirstChangeNumberVirtualAttributeProvider.java, LastChangeNumberVirtualAttributeProvider.java:
Removed all the code that was getting and passing in the parameters of ReplicationServer.getECLChangeNumberLimits().

ExternalChangeLogTest.java:
Removed now useless test ECLReplicationServerFullTest10().

JEReplicaDBTest.java:
Renamed testDbCounts() to testGetOldestNewestCSNs().
Removed now useless test testGetCountNoCounterRecords()