Bug 29844: Remove use of wantarray from Koha::Objects

Bug 29844: Remove use of wantarray from Koha::Objects

This patch removes the use of `wantarray` from the following methods in
the Koha::Objects class:
- search
- search_related

In both cases, the change is trivial. And the tests get the 'list
context' portion removed as well.

To test:
1. Apply this patch
2. Run:
   $ kshell
  k$ prove t/db_dependent/Koha/Objects.t
=> SUCCESS: Tests pass!
3. Sign off :-D

Caveat: we broke many things by removing the feature. Check follow-up
patches as well.

Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
Signed-off-by: Fridolin Somers <fridolin.somers@biblibre.com>