[FIX] account: do not call action_invoice_paid

`action_invoice_paid` should be called when the computed field
`invoice_payment_state` is set. However, the recomputation doesn't go
through `create` or `write` (since the field is protected).

A workaround  is to call it at reconciliation. Indeed, an invoice can
only be paid when it is reconciled. For invoices with an amount of zero,
we call the method at posting.

closes odoo/odoo#44259

Signed-off-by: Nicolas Martinelli (nim) <nim@odoo.com>