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

js/js.translator/testData/box/callableReference/function/classMemberOverridden.kt

@@ -0,0 +1,16 @@
+package foo
+
+open class A {
+    open fun foo(a:String,b:String): String = "fooA:" + a + b
+}
+
+class B : A() {
+    override fun foo(a:String,b:String): String = "fooB:" + a + b
+}
+
+fun box(): String {
+    val b = B()
+    var ref = A::foo
+    val result = ref(b, "1", "2")
+    return (if (result == "fooB:12") "OK" else result)
+}