[Tests] Migrate backend-independent tests from native to compiler/testData.

^KT-65979

compiler/testData/codegen/box/classDelegation/generic.kt

@@ -0,0 +1,25 @@
+/*
+ * Copyright 2010-2018 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license
+ * that can be found in the LICENSE file.
+ */
+// WITH_STDLIB
+
+import kotlin.test.*
+
+open class Content() {
+    override fun toString() = "OK"
+}
+
+interface Box<E> {
+    fun get(): E
+}
+
+interface ContentBox<T : Content> : Box<T>
+
+object Impl : ContentBox<Content> {
+    override fun get(): Content = Content()
+}
+
+class ContentBoxDelegate<T : Content>() : ContentBox<T> by (Impl as ContentBox<T>)
+
+fun box() = ContentBoxDelegate<Content>().get().toString()