When an unbuild order linked to a manufacturing order is completed, the system now automatically logs a note on the manufacturing order. This improves traceability by making it easier for users to see when and why a produced item was unbuilt.

This commit makes it so a note is logged when an unbuild order is linked
to a manufacturing order is completed.

Task: 2378831

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This change simplifies Odoo's internal testing framework so two similar test approaches now behave consistently. It helps developers write faster, more reliable tests and reduces the chance that one test affects another, without changing day-to-day user features.

Essentially make both classes be the same one, and behave like `SavepointCase`.

This change updates many automated tests to use a newer shared testing approach and fixes an issue in Belgian payroll test setup. It helps make future development safer by reducing fragile test behavior, with no expected change for day-to-day users.

Marketing Automation was updated to stay aligned with recent changes in the related mailing system. This helps ensure existing marketing automation views continue to work correctly after the underlying naming updates.

This commit is simply the follow-up of the community counterpart where we had
to rename a few XML elements.

Task ID 2202759
Community PR odoo/odoo#57000