JS: move expressions test to box tests

js/js.translator/testData/box/expression/misc/KT-740.kt

@@ -0,0 +1,22 @@
+package foo
+
+var c = 0
+
+class A() {
+    var  p = 0;
+    init {
+        c++;
+    }
+}
+
+fun box(): String {
+    ++A().p
+    if (c != 1) {
+        return "fail1: $c"
+    }
+    --A().p
+    if (c != 2) {
+        return "fail2: $c"
+    }
+    return "OK"
+}