Ghost variables are not correctly initialized in interfaces

@pcanelas is already working on this.

Since Jul 4, 2025.

Ghost variable initialization is dependent on declaring the constructor for the type the that the refinements are for. This declaration implicitly initializes int variables in a way equivalent to `@StateRefinement(to = "var(this) == 0")`
It is not possible to declare constructors for interface types as these don't have constructors. This prohibits the correct initialization of both Ghost variables and States for interfaces

```java
@ExternalRefinementsFor("java.util.List")
@Ghost("int size2")
public interface ListRefinements {

@StateRefinement(to = "size2(this) == (size2(old(this)) + 1)")
public boolean add(E elem);

@StateRefinement(from = "size2(this) > 0", to = "size2(this) == (size2(old(this)) - 1)")
public void remove(@Refinement("index >= 0") int index);
}
```
```java
public static void main(String[] args) {
List l = new ArrayList<>();

l.add(0);

int a = l.remove(0);
}
```
The error provided is `Failed to check state transitions when calling l.remove(0)`

This error messages is identical to the error message that would appear when attempting the same operation on a concrete class without a declared constructor in the Refinement definitions