Bug 29346: Biblio actions triggers

Bug 29346: Biblio actions triggers

This patch adds the trigger for the holds queue update on teh following
methods:

- C4::Biblio::DelBiblio
- C4::Biblio::ModBiblio

The ModBiblio use case could be improved by checking if itemtype is one
of the updated attributes... but it felt there was no way to do it
without some overhead. So I leave it as-is.

It also mocks the ->enqueue method in the tests that call DelBiblio and
ModBiblio to avoid breakages [1]

Tests are added to check the trigger is called.

To test:
1. Apply this patch
2. Run:
   $ kshell
  k$ prove t/db_dependent/Biblio.t
=> SUCCESS: Tests pass! It means the trigger is triggered :-D
3. Sign off :-D

[1] This breakages could be avoided if we solve Koha/BackgrounJob.pm:101
FIXME.

Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>
Signed-off-by: Nick Clemens <nick@bywatersolutions.com>
Signed-off-by: Fridolin Somers <fridolin.somers@biblibre.com>