Bug 32060: Improve performance of columns_to_str

Bug 32060: Improve performance of columns_to_str

To test:
1) Ensure the following tests pass
  t/db_dependent/Koha/Item.t
  t/db_dependent/Koha/Bibio.t
2) Go to a biblio (preferably as serial) with many items and
   click "New" -> "New item" and note down the response time.
3) Apply the patch
4) Ensure tests in 1) still pass
5) Repeat step 2), the response time should be substantially
   improved

Sponsored-by: Gothenburg University Library
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>
Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>