[BUGFIX] Do not re-sort IRRE children when sorting parent

When PID of the parent record has not changed, child records should
not be moved/sorted.

Little background helping reviewing the patch:

The 2 important changes are made in DataHandler.php line 4603
and DataHandlerHook.php around line 346.
In both cases the condition is added checking if the destination PID
of the record is the same as current one.
In that case, processing of the IRRE children is skipped.

All the changes made in the .csv files are reflecting that.
To validate them one can compare the content of the csv files
with LiveDefaultElements.csv datasets.

For example, check that sorting values in file:
core/Tests/Functional/DataHandling/IRRE/CSV/Modify/DataSet/changeParentContentSorting.csv
are the same as in the:
core/Tests/Functional/DataHandling/IRRE/CSV/DataSet/LiveDefaultElements.csv

In the Workspaces related datasets, you will see that there
are no move placeholders for IRRE children any more
(and versioned records have 0 instead ...