Correction of Sonata\Component\Event\TransformerEvents

"pre" and "post" events are all "sonata.ecommerce.pre_xxx" and shall be corrected as follows :

final class TransformerEvents
{
    const PRE_BASKET_TO_ORDER_TRANSFORM   = "sonata.ecommerce.pre_basket_to_order_transform";
    const POST_BASKET_TO_ORDER_TRANSFORM  = "sonata.ecommerce.post_basket_to_order_transform";
    const PRE_ORDER_TO_BASKET_TRANSFORM   = "sonata.ecommerce.pre_order_to_basket_transform";
    const POST_ORDER_TO_BASKET_TRANSFORM  = "sonata.ecommerce.post_order_to_basket_transform";
    const PRE_ORDER_TO_INVOICE_TRANSFORM  = "sonata.ecommerce.pre_order_to_invoice_transform";
    const POST_ORDER_TO_INVOICE_TRANSFORM = "sonata.ecommerce.post_order_to_invoice_transform";
}