Bug 36678: Index fields with non-filing characters in both versions

Bug 36678: Index fields with non-filing characters in both versions

Currently we only remove non-filing characters for sort fields, however, this can make searching difficult.
This patch adds the filing form to the index as well to aid in searching.

To test:
 0 - Setup Koha with Elasticsearch
 1 - Import the sample record on this report: "L'amour de l'art"
 2 - Search for "amour de l'art" - no results
 3 - Apply patch
 4 - Reindex
 5 - Search for "amour de l'art" - result!
 6 - Search for "title:amour de l'art" - result!

Signed-off-by: David Nind <david@davidnind.com>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
Signed-off-by: Katrin Fischer <katrin.fischer@bsz-bw.de>
(cherry picked from commit 7c20263fd0930997a8da70b8798e0ada623ac2bc)
Signed-off-by: Fridolin Somers <fridolin.somers@biblibre.com>