[IMP] website_sale: speed up loading of attributes on shop

For 10000 templates, of which around 1000 have variants, with 100 existing
attributes and 20 values for each:

- Displaying the /shop page takes 0.55s before the commit and 0.49s after.
That's a 60ms again, around 10% faster.
- The number of queries goes from 113 to 106.
- The specific line that is changed goes from 6.3% total request time down to
2.77%, so the line becomes 2.3 times faster.

closes odoo/odoo#34213

Signed-off-by: Sébastien Theys (seb) <seb@odoo.com>

addons/website_sale/controllers/main.py

@@ -278,7 +278,7 @@ class WebsiteSale(http.Controller):
         ProductAttribute = request.env['product.attribute']
         if products:
             # get all products without limit
-            attributes = ProductAttribute.search([('attribute_line_ids.value_ids', '!=', False), ('attribute_line_ids.product_tmpl_id', 'in', search_product.ids)])
+            attributes = ProductAttribute.search([('product_tmpl_ids', 'in', search_product.ids)])
         else:
             attributes = ProductAttribute.browse(attributes_ids)