[FIX] invoice_xunnel: fix XMLs download t#55131
Change the domain when searching for the partner of a downloaded XML
Change the domain of searching the partner of a XML in method
_compute_emitter_partner_id(), this was made to emulate the behavior of the same method on v.12 but the fields customer and supplier where replaced by
supplier_rank, these fields were changed due the improvements of the model.
Change the way of using
XMLSyntaxErrorto write only one import of lxml.