Replace function rand with mt_rand (prepare php 8)

dev/initdata/generate-invoice.php

dev/initdata/generate-order.php

dev/initdata/generate-product.php

dev/initdata/generate-proposal.php

dev/initdata/generate-thirdparty.php

htdocs/comm/propal/class/propal.class.php

htdocs/commande/class/commande.class.php

htdocs/compta/facture/class/facture.class.php

htdocs/contrat/class/contrat.class.php

htdocs/core/lib/functions.lib.php

.../modules/security/generate/modGeneratePassPerso.class.php

htdocs/fourn/class/fournisseur.facture.class.php

htdocs/opensurvey/fonctions.php

htdocs/projet/class/project.class.php

htdocs/supplier_proposal/class/supplier_proposal.class.php