[FIX] sql_db: use psycopg2.extensions.parse_dsn for dsn parsing

Before this patch the naive dsn parser `_dsn_to_dict` would choke
on `application_name` containing spaces or the equal sign.

closes odoo/odoo#122010

Signed-off-by: Fabien Meghazi (fme) <fme@odoo.com>