JS: move more test to box tests

js/js.translator/testData/box/examples/initializerBlock.kt

@@ -0,0 +1,13 @@
+class C() {
+    public var f: Int
+
+    init {
+        f = 610
+    }
+}
+
+fun box(): String {
+    val c = C()
+    if (c.f != 610) return "fail"
+    return "OK"
+}