[FIX] hr_holidays: allocation multi-company

As Mitchell Admin:
- Install Leaves
- General Settings > Multi Company
- Create companies A (YourCompany) and B
- Mitchell Admin should be an employee of A, not B
- Switch to company B
- Go to Leaves > Managers > All > Allocations

An AccessError is raised in `_compute_number_of_hours_display` because
we try to access `employee_id.resource_calendar_id.hours_per_day`.

After this AccessError is solved, several others are raised when
accessing a record. They are solved in this commit.

opw-2160542

closes odoo/odoo#43529

X-original-commit: 97085bf16e009ea563719385c8c7073436a1aa7e
Signed-off-by: Nicolas Martinelli (nim) <nim@odoo.com>