- Adds a default `product_id` only when the supplier info is added from
a product variant form view;
- Adds a domain on `product_id` to constrain the field to its product
template, and only if it has a product template (otherwise, there is
no domain);
- Adds a onchange to remove the product variant if the user changes the
product template and they don't match anymore because before this
commit, it was possible to have a supplier info with a variant who
doesn't belong to its supplier info's product template;
- Replaces the options `no_create_edit` by `no_create`/`no_open` as the
former doesn't work as expected.
task-2581265
Part-of: odoo/odoo#74695