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

js/js.translator/testData/box/inheritance/abstractVarOverride.kt

@@ -0,0 +1,25 @@
+package foo
+
+open abstract class A() {
+    abstract var pos: Int
+}
+
+class B() : A() {
+    override var pos: Int = 2
+}
+
+fun box(): String {
+
+    val a: A = B()
+    if (a.pos != 2) {
+        return "fail1: ${a.pos}"
+    }
+    if (B().pos != 2) {
+        return "fail2"
+    }
+    a.pos = 3;
+    if (a.pos != 3) {
+        return "fail3: ${a.pos}"
+    }
+    return "OK"
+}