@Deprecated
  default DeleteTracker postInstantiateDeleteTracker(
    ObserverContext<? extends RegionCoprocessorEnvironment> ctx, DeleteTracker delTracker)
    throws IOException {
    return delTracker;
  }
Called after the ScanQueryMatcher creates ScanDeleteTracker. Implementing this hook would help
in creating customised DeleteTracker and returning the newly created DeleteTracker
<p>
Warn: This is used by internal coprocessors. Should not be implemented by user coprocessors
@param ctx        the environment provided by the region server
@param delTracker the deleteTracker that is created by the QueryMatcher
@return the Delete Tracker
@deprecated Since 2.0.0, will be removed in 4.0.0. Visibility label feature still use this
            method, so it can not be removed in 3.0.0
hbase-server/src/main/java/org/apache/hadoop/hbase/coprocessor/RegionObserver.java