[IMP] website_links: performance on search_read

The widget Selectbo was performing a search_read on every field while
only using the fields id and name. This search_read has become very costly
in the latest version due to some new fields.
We now limit the search_read to the useful fields.

closes odoo/odoo#45654

Signed-off-by: Rémi Rahir (rar) <rar@odoo.com>