Fix for navigation issues introduced by MR!47998

Draft. Addressing the reset of index_ref column on auto_flush when using TMemFile (as observed in Derivation 22.0.50). Code is still in rough shape, many parts only commented out to allow better review. Cleanup before merge.

Still running local tests to check that this addresses the problem. Still needs to address conditions test. known to be broken. For now this is meant to collaborate with @mnowak and @amete as fixing the underlying problem is urgent.