JS: move more test to box tests

js/js.translator/testData/box/simple/simpleInitializer.kt

@@ -0,0 +1,12 @@
+package foo
+
+class Test() {
+    var a: Int
+    init {
+        a = 3
+    }
+}
+
+fun box(): String {
+    return if (Test().a == 3) "OK" else "fail"
+}