04ac4b71a3
In the FIR generator, the `AbstractElement` class was used to represent either an element type without type arguments applied (using the `Element` subclass), or an element type with applied type arguments (using the `ElementWithArguments` subclass). Instead, it is more logical to use the `Element` class to always represent a non-parameterized element type, and for a parameterized element type use the `ElementRef` class, just like we do in the IR generator.