Bug 35507: Plugins.t - Mock SessionStorage, remove KitchenSink

Bug 35507: Plugins.t - Mock SessionStorage, remove KitchenSink

Removing the CGI::Session behavior to auto-commit by mocking
SessionStorage makes that the $plugin->test_template does no
longer commit.

Since KitchenSink includes a CREATE TABLE, removing that code
removes the second implicit commit. We might move that code
to its own script?

Adds a missing rollback too at the end.

Test plan:
Run prove t/db_dependent/Koha/Plugins/Plugins.t
Verify that no records got added to plugin_data/methods table.

Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
Signed-off-by: Katrin Fischer <katrin.fischer@bsz-bw.de>