`implements ToBeGenerated` type shows up as a `CLASS` kind rather than an `INTERFACE`.

Take the following java source

```java
class Subject implements ToBeGenerated {}
```

Consider the case where `ToBeGenerated` will be generated by some processor, but has not been generated yet.

When processing with Javac annotation processing, `ToBeGenerated` will still show up as an interface of `Subject` via [`TypeElement#getInterfaces()`](https://docs.oracle.com/javase/8/docs/api/javax/lang/model/element/TypeElement.html#getInterfaces--) even though it has not been generated yet.

In KSP the `KSClassDeclaration` API does not distinguish between the super class and super interfaces, they are all combined into a single API, `KSClassDeclaration#superTypes()`. Thus, we need to `superType.resolve()` each super type, then cast `as? KSClassDeclaration`, and finally check `KSClassDeclaration#classKind()` to determine if its a `CLASS` or `INTERFACE` kind. However, the issue here is that `ToBeGenerated` shows up as `CLASS` rather than `INTERFACE` kind.

Ideally, KSP would match Javac here and treat the missing type, `ToBeGenerated`, as an `INTERFACE` kind since it appears under `implements` rather than `extends` declaration.

(Note: I realize this is a bit of an edge case (as everything works fine after `ToBeGenerated` has been generated) but it helps with libraries like `XProcessing` trying to support both Javac and KSP if things behave similar between the two.)