[FIX] base_vat: Albania

The module `vatnumber` (which is not maintained anymore) uses an
incorrect validation method for Albanian VAT numbers. Therefore, we use
the library `stdnum`, on which `vatnumber` relies for most cases.

opw-1912680

closes odoo/odoo#29280

addons/base_vat/models/res_partner.py

@@ -361,3 +361,10 @@ class ResPartner(models.Model):
             return int(vat[9]) == c1 and int(vat[10]) == c2
 
         return False
+
+    def check_vat_al(self, vat):
+        try:
+            import stdnum.al
+            return stdnum.al.vat.is_valid(vat)
+        except ImportError:
+            return True