This update modernizes the Resource scheduling area and related integrations so calendars, leave intervals, payroll, holidays, project issues, and stock calendars continue to work correctly on the newer Odoo API. It also refreshes tests from older YAML cases to Python unit tests, improving reliability for future changes.

[Resource]: MIgrate to new api.

Task: https://www.odoo.com/web?#id=12717&view_type=form&model=project.task&menu_id=3942&action=327
Pad: https://pad.odoo.com/p/r.HVRfO2VpgIBXW4xh

This pull request migrates several stock-related modules to Odoo's newer internal framework and cleans up related code. It improves maintainability for inventory, sales stock flows, purchasing, product pricing history, dropshipping, landed costs, and stock accounting while preserving business functionality.

<strong>Task:</strong> https://www.odoo.com/web#id=13132&view_type=form&model=project.task&menu_id=3942&action=327
<strong>Pad:</strong> https://pad.odoo.com/p/r.dTbdXwkcpfrYp0Ww

This update reorganizes and modernizes several inventory-related add-ons, including stock accounting, dropshipping, and landed costs. It should make these areas easier to maintain and evolve, with limited direct change for day-to-day users.

<strong>Task:</strong> https://www.odoo.com/web#id=13132&view_type=form&model=project.task&menu_id=3942&action=327
<strong>Pad:</strong> https://pad.odoo.com/p/r.dTbdXwkcpfrYp0Ww