This update modernizes how Odoo manages background database work and business transaction state. It should make the platform easier to maintain and more reliable without changing day-to-day user workflows.

Linked to https://github.com/odoo/odoo/pull/75598.

The PLM bill of materials structure report was cleaned up by removing unused display logic and obsolete styling hooks. This keeps the report behavior consistent while making future maintenance easier and reducing the risk of confusing report differences.

The code of `_reload_report_type` for plm wasn't
 correct (there isn't a `report_type === 'bom_cost'` ). Then
 remove this code to keep the same behaviour.
Then the classes `o_mrp_bom_ver` and `o_mrp_ecos`
wasn't used, then remove it.
Also simplify template because of `_get_extra_column_count`.

See odoo/odoo#75041
See odoo/upgrade#2750