Bug 37357: Map @ to 00 for control field select lists

Bug 37357: Map @ to 00 for control field select lists

This change adds the existing @ to 00 mapping for control fields
to work for authorized value select lists as well.

Test plan:
0. Apply the patch
1. koha-plack --reload kohadev
2. Make 001 subfield @ mandatory and give
it an authorised value of branches for Default framework
3. Go to the New record editor for a Default record
4. Click "Save"
5. Note that the editor prompts you to fill in the 001 field
6. Fill in required fields and click "Save"
7. Note that all data is captured correctly
8. prove t/db_dependent/Koha/UI/Form/Builder/Biblio.t

To prove that this wouldn't work without the patch, try the test
plan on a different branch without this patch. You won't be prompted
to fill in mandatory fields and the record will just save (or if a
possible duplicate is detected it will just redirect you back to an empty
editor)

Signed-off-by: David Nind <david@davidnind.com>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
Signed-off-by: Katrin Fischer <katrin.fischer@bsz-bw.de>