Bug 21201: Replace C4::Items::GetItemnumbersForBiblio calls

Bug 21201: Replace C4::Items::GetItemnumbersForBiblio calls

Those calls to C4::Items::GetItemnumbersForBiblio can be replaced with
    my @itemnumbers = Koha::Items->search({ biblionumber => $biblionumber})->get_column("itemnumber")

Test plan:
- Use the GetAvailability service of ILS-DI
- Try to place a hold on an item that is available and another one
- Use the batch record deletion tool to remove record with and without items.

Signed-off-by: Josef Moravec <josef.moravec@gmail.com>
Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Signed-off-by: Nick Clemens <nick@bywatersolutions.com>