Bug 34725: Remove use of onclick for OPAC cart

Bug 34725: Remove use of onclick for OPAC cart

This patch moves the click handler in the OPAC cart from the inline HTML
and out to an existing <script> element.

Test plan:
0. Apply the patch
1. Go to http://localhost:8080/cgi-bin/koha/opac-search.pl?idx=&q=test&weight_search=1
2. Add the results to the cart
3. Click on the "Cart"
4. One by one click on the title of each row
5. Notice how the parent window changes to the detail record for that title

Signed-off-by: Pedro Amorim <pedro.amorim@ptfs-europe.com>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>