JS: move expressions test to box tests

js/js.translator/testData/box/expression/when/whenWithOneStmWhen.kt

@@ -0,0 +1,22 @@
+package foo
+
+
+fun box(): String {
+    var result = "fail1"
+    val i = 1
+    when (i) {
+        1 ->
+            when (i) {
+                1 ->    result = "OK"
+                else -> result = "fail2"
+            }
+
+        else ->
+            when (i) {
+                1 ->    result = "OK"
+                else -> result = "fail3"
+            }
+    }
+
+    return result
+}