This update modifies Odoo templates to align with upcoming OWL3 requirements, specifically by adding `.this` to template variables. This change is necessary to correctly target component variables within the Odoo rendering context, ensuring compatibility with the new OWL3 framework. The changes were made manually to ensure proper implementation.

In preparation for OWL3, where template variables will need to use `.this` to target component variables, we add `.this` to template variables that are targetting the component.

Community PR: https://github.com/odoo/odoo/pull/254865
Script PR: odoo/odoo#247965

task: OWL3 prep - add this. to template variables

This update streamlines the way Odoo calculates task overlaps, resulting in faster and more efficient processing. The change utilizes a direct SQL query and a single calculation function, replacing a more complex internal ORM approach. This improves overall performance and responsiveness for task scheduling.

Use a simple SQL and call `_where_calc` once instead of using internal ORM methods.