Support KClass.nestedClasses

compiler/testData/codegen/boxWithJava/reflection/nestedClasses/J.java

@@ -0,0 +1,10 @@
+public class J {
+    public class Inner {}
+
+    public static class Nested {}
+
+    private static class PrivateNested {}
+
+    // This anonymous class should not appear in 'nestedClasses'
+    private final Object o = new Object() {};
+}

compiler/testData/codegen/boxWithJava/reflection/nestedClasses/K.kt

@@ -0,0 +1,7 @@
+import kotlin.test.assertEquals
+
+fun box(): String {
+    assertEquals(listOf("Inner", "Nested", "PrivateNested"), J::class.nestedClasses.map { it.simpleName!! }.toSortedList())
+
+    return "OK"
+}