Delete kotlin.jvm.internal.KObject

It was supposed to be used in reflection but the benefits do not outweigh the
cost of KT-6951

 #KT-3223 Fixed
 #KT-6951 Fixed

compiler/testData/asJava/lightClasses/nullabilityAnnotations/Synthetic.java

@@ -1,9 +1,9 @@
-public final class Synthetic implements kotlin.jvm.internal.KObject {
+public final class Synthetic {
     private final void foo() { /* compiled code */ }
 
     public Synthetic() { /* compiled code */ }
 
-    public final class Inner implements kotlin.jvm.internal.KObject {
+    public final class Inner {
         public final void test() { /* compiled code */ }
 
         public Inner() { /* compiled code */ }