In the IR generator, we had a so-called `ConfigModel` with classes like
`ElementConfig` and `FieldConfig` that we deal with during
tree configuration in `IrTree.kt`, and another kind of model called
just `Model` that included the `Element` and `Field` classes
correspondingly. Those were used for actual code generation.
After configuration, `ConfigModel` was transformed to `Model` and
then the code generation was performed using `Model`.
This architecture is overly complicated and results in massive code
duplication. Most `ElementConfig` and `FieldConfig` properties had
exactly the same counterparts in `Element` in `Field` classes.
So, if you wanted to add a new feature to the tree generator, you had to
add a property to both `ConfigModel` and `Model`.
Turns out we can do just fine with only one kind of model.
Sergej Jaskiewicz
6ac4cd5973