JS: move more test to box tests

js/js.translator/testData/box/safeCall/safeAccess.kt

@@ -0,0 +1,22 @@
+package foo
+
+class A() {
+    var c = 3
+}
+
+fun box(): String {
+    var a1: A? = A()
+    var a2: A? = null
+    a1?.c = 4
+    a2?.c = 5
+    if (a1?.c != 4) {
+        return "fail1"
+    }
+    a2 = a1
+    a2?.c = 5
+
+    if (a2?.c != 5) return "fail2"
+    if (a1?.c != 5) return "fail3"
+
+    return "OK"
+}