Reflection: add KClass.{supertypes,superclasses,allSupertypes,allSuperclasses}

Some things are not implemented yet for allSupertypes, such as KType->Type
mapping of types and generic substitution of built-in types

core/builtins/src/kotlin/reflect/KClass.kt

@@ -63,6 +63,11 @@ public interface KClass<T : Any> : KDeclarationContainer, KAnnotatedElement, KCl
      */
     public val typeParameters: List<KTypeParameter>
 
+    /**
+     * The list of immediate supertypes of this class, in the order they are listed in the source code.
+     */
+    public val supertypes: List<KType>
+
     /**
      * Returns `true` if [other] is a [KClass] instance representing the same class on a given platform.
      *