Bug 24031: Add plugin hook after_hold_create

Bug 24031: Add plugin hook after_hold_create

It is called after a hold has been placed

Test plan:
1. Write a plugin that implements only after_hold_create (see
   `perldoc Koha::Plugins` for implementation details). Install it and
   enable it
2. Place a hold and verify that your plugin method has been called with
   the right parameters

Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>
Signed-off-by: Pasi Kallinen <pasi.kallinen@koha-suomi.fi>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>