JS: move expressions test to box tests

js/js.translator/testData/box/expression/misc/KT-5058.kt

@@ -0,0 +1,25 @@
+package foo
+
+fun test():Any {
+    val a: Any = "OK"
+    val f: Any =
+            if (true) {
+                when {
+                    false -> "1"
+                    ((a as? String)?.size ?: 0 > 0) -> a
+                    else -> "2"
+                }
+            }
+            else {
+                "3"
+
+            }
+
+    return f
+}
+
+fun box(): Any {
+    var result = test()
+    return result
+}
+