[FIX] hr_expense: set the expense account and employee on generated move lines

Currently, when posting accounting entries from an expense report, the accounts set on the expense entries were not taken over in the account move lines. Also, the employee was not set as the vendor of the purchase receipt (account move).

This PR makes sure that both the accounts on the expenses, as well as the vendor (employee) is set on the account move created from an expense report.
Tests added as well.

closes odoo/odoo#102570

Signed-off-by: Quentin De Paoli <qdp@odoo.com>