Filter HFiles based on TTL

In ScanWildcardColumnTracker we have

 
  this.oldestStamp = EnvironmentEdgeManager.currentTimeMillis() - ttl;

  ...

  private boolean isExpired(long timestamp) {
    return timestamp < oldestStamp;
  }

but this time range filtering does not participate in HFile selection. In one real case this caused next() calls to time out because all KVs in a table got expired, but next() had to iterate over the whole table to find that out. We should be able to filter out those HFiles right away. I think a reasonable approach is to add a "default timerange filter" to every scan for a CF with a finite TTL and utilize existing filtering in StoreFile.Reader.passesTimerangeFilter.