Bug 24715: Cache repeatable subfield in TransformKohaToMarc

Bug 24715: Cache repeatable subfield in TransformKohaToMarc

Implemented by calling GetMarcSubfieldStructure and improving
_check_split which may check repeatability in a specific framework,
and return the framework hash.

Test plan:
Run t/db_dependent/Biblio/TransformKohaToMarc.t
Optionally, follow the test plan of bug 21800#comment7.

Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Signed-off-by: Ere Maijala <ere.maijala@helsinki.fi>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>