[FIX] product: create variants in multi-company

- Install stock module
- Activate multi-company and variants
- Create a second company
- Create a product with 2 variants
- Create a picking with the product for both companies
- Add an attribute on the product with 2 values
- Save

An AccessError is raised on `stock.move`.

It arises because the field `product_qty` on `stock.move` must be
recomputed but is on a record in a different company.

The `try` / `except` clause doesn't protect against the recomputation.
Indeed, what happens is:
- try to unlink in batch => AccessError due to recomputation
- try to unlink individually => AccessError due to recomputation
- try to write individually => the field couldn't be recomputed before
(flagged as dirty), so try again to recompute => AccessError

We perform the operation as sudo, and take care of checking the access
rights beforehand.

opw-2009450

closes odoo/odoo#34369

Signed-off-by: Nicolas Martinelli (nim) <nim@odoo.com>