[FIX] hr_recruitment: separate contacts for employees

The fix introduced in odoo/odoo#114903 created another issue: changing
the work email would change the private email also, breaking the
seperation of the contacts for the employee.

The initial behavior was correct:
 - a res.partner for the work details (email, phone, etc.)
 - a res.partner (of type private) for the personal details of the
employee.

task-3284664

closes odoo/odoo#119460

Signed-off-by: Kevin Baptiste <kba@odoo.com>