amount_generator: speed up property initialization of generated amounts

By default, Base._edit first tests each property with getProperty, not to
modify the object when values don't change. Here, getProperty costs a lot
(in particular for categories) and rarely/never avoids the use of setters.

So here, the main gain is to do something like _edit(force_update=1).
As an additional small optimization, we directly use _setProperty instead of
_edit. We also stop copying int_index from the Amount Generator Line because
it's not useful enough:
- float_index may be used instead
- or dependency-based sorting is enough
- as a last resort, properties can be fetched directly from the causality
  value, or dynamically with asPredicate and mapped_value_property_list

product/ERP5/mixin/amount_generator.py

@@ -477,13 +477,11 @@ class AmountGeneratorMixin:
         amount._setCategoryList(property_dict.pop('category_list', ()))
         if amount.getQuantityUnit():
           del property_dict['quantity_unit']
-        amount._edit(
-          quantity=quantity,
-          # XXX Are title, int_index and description useful ??
-          title=self.getTitle(),
-          int_index=self.getIntIndex(),
-          description=self.getDescription(),
-          **property_dict)
+        amount._setQuantity(quantity)
+        amount._setTitle(self.getTitle())
+        amount._setDescription(self.getDescription())
+        for x in property_dict.iteritems():
+          amount._setProperty(*x)
         # convert to default management unit if possible
         amount._setQuantity(amount.getConvertedQuantity())
         amount._setQuantityUnit(amount.getResourceDefaultQuantityUnit())