[FIX] account: send invoices with the right name

The mail_notification_paynow template expects a model_description
parameter or defaults to the model _description, "Journal Entries".
We add, similar to 4a3fd02a on sale.order, a type_name field to
get the correct type name in an extensible way.

Similar to 8c91b193, 65b6375c.

opw 2120545

closes odoo/odoo#40216

Signed-off-by: Nans Lefebvre (len) <len@odoo.com>