Bug 24052: Fix Koha/XSLT/Base.t

Bug 24052: Fix Koha/XSLT/Base.t

Moving the separate small attachments into the test script.
Creating them now as temporary files or code fragments.
Deleting original files.

Since Breeding.t also used one of these files, a similar change was made in
that script.

Test plan:
Run t/db_dependent/Koha/XSLT/Base.t. Should pass now.
Run t/db_dependent/Breeding.t again.
Git grep on XSLT_Handler. You should only find release notes.

Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Signed-off-by: Owen Leonard <oleonard@myacpl.org>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>