Change the default recipient of the simulation link to be the employee's
work email address, instead of the private email address.
Currently the private email of employees is used for this but this doesn't
work because mail.compose.message does not allow allow private partners
to be configured as recipients. Secondly, it also just makes sense to send
work-related email to the work email address.
In addition, since a partner is automatically created when sending an
email to this work email address (which is currently a string field, a new
field is created to keep track of this partner, in addition to other
partners that might be linked to employee.
task-2790044
closesodoo/odoo#95655
Related: odoo/enterprise#27808
Signed-off-by: Kevin Baptiste <kba@odoo.com>