Unstable output order

[litghost]

The code generator generate functions in an order that is dependent on the hash order from python, which is unstable. This causes unneeded diffs when re-running the generator.

In generally, function output order should be constant when possible.

[duck2]

The complex types are sorted in the schema according to tree height. Maybe the order between types with equal tree height is varying? Should we also sort alphanumerically?