Bug 34230: Add part_name and part_number to subscription search results

Bug 34230: Add part_name and part_number to subscription search results

This adds biblio.part_name and biblio.part_number to the SELECT of
SearchSubscriptions in order to be able to display the information in
the results list. It does not affect search.

To test:
* Add one or more subscriptions
* Make sure at least one is linked to a title with 245$abnp
* Verify that the result list only shows 245$ab
* Apply patch
* Verify full title information is now shown

Signed-off-by: Sam Lau <samalau@gmail.com>
Signed-off-by: Michaela Sieber <michaela.sieber@kit.edu>
Signed-off-by: Chris Cormack <chris@bigballofwax.co.nz>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>