Handle 035 mapping to formerIds for MARC Holdings transformation

The default MARC Holdings mapping rules use an entity mapping to map 035 -> formerIds array. The current MARC transformation handling in the tools do not handle this correctly. Current workaround is to change from an entity mapping to a normal target mapping. The tools should be updated to work with the default mapping rules.

Start by locating the MARC Holdings transformation code and the handling of default mapping rules in the tools. Reproduce the 035-to-formerIds case using the default entity mapping, then compare it with the target-mapping workaround. Done means the default mapping correctly produces the formerIds array without requiring a workaround.

Written by the indexing model from the issue text.