Evaluate DataContainer size method invocations to make sure they make sense

In an attempt to improve spliterator performance we try to give it an estimate of the size. Currently this is calling DataContainer.size which in fact is anything but performant as it requires O(N) time to make sure to not count entries that are expired. We should instead call sizeIncludingExpired as this is O(1) and this is a best guess anyways, doesn't need to be exact.