And define the mentioned property sheet on Template Tool portal type. This is
necessary as while running the post_upgrade constaint 'migrate_catalog_constaint',
the script will run only if the portal_type it is defined on is indexed in the
catalog. But if we define it on 'Catalog Tool' portal type, it won't be called
as it can't be indexed before migration, so it is better to define on 'Template Tool'.

If needed, we can change the name of the property sheet to honor naming
conventions. Also, it makes more sense to have migration script in portal
skin 'erp5_upgrader' as it is also a part of upgrading erp5.

** Add test for migration of catalog via portal_alarm

** Also, update the other tests where it was taken for granted that
there are no constraint for 'post_upgrade', as now we have added
an extra post_upgrade constraint in erp5_upgrader bt5.