Bug 22339: Fix search field mappings of MARC fixed fields

Bug 22339: Fix search field mappings of MARC fixed fields

Fixes handling of /0 selector in addition to several fixed field positions. Note that ff7-01-02 is in fact 00-01 in Zebra and that has been replicated here.

Test plan:
1. Before applying a patch, check from Elasticsearch (e.g. localhost:9200/koha_biblios/_search?q=_id:123) what is indexed in Elasticsearch for a record for date-entered-on-file, ff7-00, ff7-01, ff7-02 and lleader.
2. Apply the patch, update database and save the record again.
3. Verify that the contents of the forementioned fields is now correct in Elasticsearch.
4. Verify that tests pass:  prove -v t/Koha/SearchEngine/Elasticsearch.t

Signed-off-by: Björn Nylén <bjorn.nylen@ub.lu.se>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
Signed-off-by: Nick Clemens <nick@bywatersolutions.com>