Bug 30756: Ground work for improving Koha_Authority.t

Bug 30756: Ground work for improving Koha_Authority.t

Move stuff into two subtests.

Test plan:
Run t/db_dependent/Koha_Authority.t.
If you have no imported auths, you will still see skips.

Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Signed-off-by: David Nind <david@davidnind.com>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>
(cherry picked from commit 96867a4fdcde290a260085b38b5e285c455828db)

Signed-off-by: Lucas Gass <lucas@bywatersolutions.com>