This change refreshes internal performance test benchmarks for the mail testing area so they match the current application behavior. It also reorganizes shared test setup to keep the test code easier to maintain, with no expected impact on end users.

The QWeb template documentation now marks several older loop helper variables and integer loop usage as deprecated. This helps developers avoid relying on rarely used shortcuts that can be calculated directly, reducing future maintenance risk.

These variables aren't used in Odoo and can be easily computed
anyway.

Description of the issue/feature this PR addresses:

Current behavior before PR:

Desired behavior after PR is merged:




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This update adapts several business apps to a shared system setting for decimal precision, replacing older module-level setup. It keeps calculations and displayed numeric values consistent while simplifying maintenance across payroll, manufacturing, quality, rental, subscription, and invoicing features.

<b> Task: </b> https://www.odoo.com/web?#id=48198&action=333&active_id=131&model=project.task&view_type=form&menu_id=4720
<b> Pad:</b> https://pad.odoo.com/p/r.b7203e0259fe5f6c20fb86a7abad9f21

Community PR odoo/odoo#25467