Fix cases where Category name is translated and domain breaks

In non-english interfaces the `domain="[('category_id.name', '=', 'Weight')]"` returns nothing since `category_id.name == 'Poids'`

There does not seem to be any way to refer to model datas within `arch` of a view, so `product_uom_categ_kgm_ref` was created to only point at the ID of `product.product_uom_categ_kgm`