Ignore the don't needs view types on _build_onchange_specs

1. Overwrite fields_get function to added a dynamic fields to sale.order.line named d_field_345
2. And bind on_change event to d_field_345 use view field tag

current:
 Error reported when i open the sale.order form, KeyError means not found d_field345 in sale.order.line
 that error in onchange method from client post
expect:
 nested form(embedded form tag in field order_line) don't need load on master form view