[18.0][ADD]fleet_vehicle_assignation_log_datetime: add new module Replaces #184

[rpsjr]

Replaces #184

Motivation
The standard driver assignation log in Odoo tracks assignments by date, which lacks the precision needed to determine responsibility for time-sensitive events like traffic infractions. This module introduces datetime precision to solve this problem.

Implementation
Adds datetime_start and datetime_end fields to fleet.vehicle.assignation.log.
Replaces the original date fields in the view with the new datetime fields for a better user experience.
Keeps the original date fields invisible and synchronized via onchange methods to ensure backward compatibility.
Overrides fleet.vehicle.write() to set the datetime_start and datetime_end to the exact moment a driver is changed from the vehicle's form view.

[github-actions]

There hasn't been any activity on this pull request in the past 4 months, so it has been marked as stale and it will be closed automatically if no further activity occurs in the next 30 days.
If you want this PR to never become stale, please ask a PSC member to apply the "no stale" label.