[Test] Move KotlinAgainstKotlin tests under BlackBoxCodegen tests

compiler/testData/codegen/box/compileKotlinAgainstKotlin/doublyNestedClass.kt

@@ -0,0 +1,20 @@
+// MODULE: lib
+// FILE: A.kt
+
+package aaa
+
+class A {
+    class B {
+        class O {
+          val s = "OK"
+        }
+    }
+}
+
+// MODULE: main(lib)
+// FILE: B.kt
+
+fun box(): String {
+    val str = aaa.A.B.O().s
+    return str
+}