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/codegen/boxWithStdlib/regressions/getGenericInterfaces.kt

@@ -1,7 +1,5 @@
 // KT-4485 getGenericInterfaces vs getInterfaces for kotlin classes
 
-import kotlin.jvm.internal.KObject
-
 class SimpleClass
 
 class ClassWithNonGenericSuperInterface: Cloneable
@@ -10,10 +8,6 @@ class ClassWithGenericSuperInterface: java.util.Comparator<String> {
     override fun compare(a: String, b: String): Int = 0
 }
 
-class ExplicitKObject: java.util.Comparator<String>, KObject {
-    override fun compare(a: String, b: String): Int = 0
-}
-
 fun check(klass: Class<*>) {
     val interfaces = klass.getInterfaces().toList()
     val genericInterfaces = klass.getGenericInterfaces().toList()
@@ -26,6 +20,5 @@ fun box(): String {
     check(javaClass<SimpleClass>())
     check(javaClass<ClassWithNonGenericSuperInterface>())
     check(javaClass<ClassWithGenericSuperInterface>())
-    check(javaClass<ExplicitKObject>())
     return "OK"
 }