Bug 26180: Add descending option to rebuild_elasticsearch.pl

Bug 26180: Add descending option to rebuild_elasticsearch.pl

While the ES index is incremental and provides results as it commits, we currently index from the oldest records to the newest.

This patch provides the option to go the other direction

To test:
 1 - Have ES setup and running for Koha
 2 - perl misc/search_tools/rebuild_elasticsearch.pl -v -v -b
 3 - Note the biblios index from number 1 the end
 4 - perl misc/search_tools/rebuild_elasticsearch.pl -v -v -a
 5 - Notice the same
 6 - Apply patch
 7 - perl misc/search_tools/rebuild_elasticsearch.pl -v -v -b
 8 - Still in ascending order
 9 - perl misc/search_tools/rebuild_elasticsearch.pl -v -v -b --desc
10 - Now records index in descending order
11 - perl misc/search_tools/rebuild_elasticsearch.pl -v -v -a
12 - Still ascending
13 - perl misc/search_tools/rebuild_elasticsearch.pl -v -v -a --desc
14 - Now descending

Signed-off-by: Séverine QUEUNE <severine.queune@bulac.fr>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
JD amended patch: fix typo "inde" vs "index" and add commit body

Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>