Bug 30879: Add biblionumber as a sorting option in MARC21

Bug 30879: Add biblionumber as a sorting option in MARC21

This patch updates the Local-Number indexing by adding a zeropad option
to Zebra indexing and adding this to the mapping files

It also updates C4/Search.pm to allow biblionumber as an option

To test:
1 - Apply patches
2 - copy etc/zebradb/marc_defs/marc21/biblios/biblio-zebra-indexdefs.xsl to /etc/koha/zebradb/marc_defs/marc21/biblios/biblio-zebra-indexdefs.xsl
3 - Restart all, reindex zebra
4 - Browse to: http://localhost:8081/cgi-bin/koha/catalogue/search.pl?idx=kw&q=a&sort_by=biblionumber_dsc&count=20
5 - Confirm records sorted correctly
6 - Browse to http://localhost:8081/cgi-bin/koha/catalogue/search.pl?idx=kw&q=a&sort_by=biblionumber_asc&count=20
7 - Confirm records sorted correctly

Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>