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

^KT-65979

compiler/testData/codegen/box/boxing/boxing0.kt

@@ -0,0 +1,23 @@
+/*
+ * 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.*
+
+class Box<T>(t: T) {
+    var value = t
+}
+
+fun box(): String {
+    val box: Box<Int> = Box<Int>(17)
+    if (box.value != 17) return "FAIL 1: ${box.value}"
+
+    val nonConst = 17
+    val box2: Box<Int> = Box<Int>(nonConst)
+    if (box2.value != 17) return "FAIL 1: ${box2.value}"
+
+    return "OK"
+}
+