The structure of the product.{product,template} form is the following:

product.product_template_form_view* (both)
|-- product.product_template_only_form_view* (template)
|   \-- stock.product_template_form_view_procurement_button
|
|-- product.product_normal_form_view* (product)
|   \-- stock.product_form_view_procurement_button
|
\-- stock.view_template_property_form (both)

Previous view was adding weight, volume fields on both view with a attrs that
applies only to the product.template (display only if no template).

This means that the weight was not displayed on product.product form if opened
from a Many2one (using the default product.product view) while the attrs should
not hide it.

Closes #16541
Fixes #16428