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

^KT-65979

compiler/testData/codegen/box/basics/unchecked_cast4.kt

@@ -0,0 +1,28 @@
+/*
+ * Copyright 2010-2019 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.*
+
+fun box(): String {
+    CI1I2().uncheckedCast<CI1I2>()
+    CI1I2().uncheckedCast<OtherCI1I2>()
+
+    assertFailsWith<ClassCastException> {
+        Any().uncheckedCast<CI1I2>()
+    }
+
+    return "OK"
+}
+
+fun <R : C> Any?.uncheckedCast() where R : I1, R : I2 {
+    this as R
+}
+
+interface I1
+interface I2
+open class C
+
+class CI1I2 : C(), I1, I2
+class OtherCI1I2 : C(), I1, I2