Eng 6607 - Add support for truncate table to DR2

A way too roundabout way. This code is a tail wagging a dog that should have been sent to the farm long ago.
Prior to this change, DummyUndoQuantum.h was dead code that was accidentally missed by a code purge.
Here it is being resurrected just so that that we don't have to replicate the one line "release" function -- which just delegates to persistenttable::truncateTableRelease -- and risk missing future changes there by the lack of abstraction.
Alternatives:
    - put a comment in PersistentTableUndoTruncateTableAction::release along the lines of
"// Rather than change this method, change truncateTableRelease for consistency with the no-undo case" and call truncateTableRelease directly here OR
    - make PersistentTableUndoTruncateTableAction's destructor and release functions public (or be-friend persistenttable) and call release on a stack-based instance, here.
Benefits:
    - DummyUndoQuantum.h can go away.
    - Avoids allocating a short-lived Pool for the sole purpose of allocating one tiny object in it.