Bug 34234: Respect display_order in additem.tt and detail.tt

Bug 34234: Respect display_order in additem.tt and detail.tt

1. APPLY PATCH
2. EnableItemGroups
3. Find a record and add some new item groups with display orders that are different from the order in which the groups were added
4. Check the checkbox next to one or more items and click the link to "Add/move to item group"
5. Ensure display order is correct
6. Now add a new item to the record and scroll down to the dropdown underneath "+ Add to item group"
7. Display order should be correct.

Signed-off-by: David Nind <david@davidnind.com>
Signed-off-by: Victor Grousset/tuxayo <victor@tuxayo.net>
Signed-off-by: Katrin Fischer <katrin.fischer@bsz-bw.de>
(cherry picked from commit bcfc786f17fad8b7c866ee6063d2953d7b5d925d)
Signed-off-by: Fridolin Somers <fridolin.somers@biblibre.com>