JS: create new common directory for all generated tests, migrate several tests there

js/js.translator/testData/box/classObject/setVar.kt

@@ -0,0 +1,26 @@
+package foo
+
+class A {
+    var a = 3
+    companion object {
+        var a = -2
+    }
+}
+
+
+fun box(): String {
+    A.a = 2
+    if (A.a != 2) return "A.a != 2, it: ${A.a}"
+
+    val a = A
+    a.a = 3
+    if (a.a != 3) return "a = A; a.a = 3; a != 3, it: ${a.a}"
+
+    if (A().a != 3) return "A().a != 3, it: ${A().a}"
+
+    val x = A()
+    x.a = 4
+    if (x.a != 4) return "x = A(); x.a = 4; x.a != 4, it: ${x.a}"
+
+    return "OK"
+}