[IMP] hr_expense: add accounting_date in expense

Add a related field `accounting_date` in the expense to the expense
report.

 - Should represent the accounting_date field from the expense report
 linked to this expense
 - Only visible if the status of the report is approve, post or done
 - Only visible if the user has at least the Accounting > Auditor access
 right level
 - Should be in read-only
 - Should be stored

closes odoo/odoo#48238

Taskid: 2221668
Signed-off-by: Yannick Tivisse (yti) <yti@odoo.com>