Bug 31482: Label creator does not call barcodedecode

Bug 31482: Label creator does not call barcodedecode

The label creator can accept a list of either itemnumbers or item barcodes.
In the case that the list of composed of barcodes, those barcodes should be
passed though barcodedecode before the lookup is performed.

Test Plan:
1) Apply this patch
2) Download and install the Barcode Transformer plugin
   https://github.com/bywatersolutions/koha-plugin-barcode-transformer/releases/
3) Go to the plugin configuration page, set the configuration to the example configuration from the same page
4) On the "New label batch" page of the Label creator,,
   type in some valid barcodes, but prefix them with X and postfix them with Y, e.g. X123456Y
5) Submit the form
6) Note the items are added to the label batch!

JK: Remove unnecessary if $number check, barcodedecode already does this

Signed-off-by: Joonas Kylmälä <joonas.kylmala@iki.fi>
Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>