Bug 15048: Index all possible searched subfields for index-term-genre

Bug 15048: Index all possible searched subfields for index-term-genre

Currently we only index a - but we can setup the system such that avxyz are searched

To test:
 1 - define both a 655$a *and* 655$x value in a bib, save, reindex
 2 - Set system preferences:
      TraceSubjectSubdivisions: Include
      TraceCompleteSubfields: Force
 3 - View the record edited above in the opac
 4 - Click on the subject heading
 5 - No results found
 6 - Copy zebra files:
  sudo cp ./etc/zebradb/marc_defs/marc21/biblios/biblio-koha-indexdefs.xml \
  /etc/koha/zebradb/marc_defs/marc21/biblios/biblio-koha-indexdefs.xml
  sudo cp etc/zebradb/marc_defs/marc21/biblios/biblio-zebra-indexdefs.xsl \
  /etc/koha/zebradb/marc_defs/marc21/biblios/biblio-zebra-indexdefs.xsl
 7 - restart all and reindex
 8 - Click on the subject heading in OPAC
 9 - Sucess!
10 - Repeat with other fields (vyz)
11 - Repeat under ES, reindexing and resetting mappings

Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>