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

js/js.translator/testData/box/extensionFunction/extensionOnClassWithExplicitAndImplicitReceiver.kt

@@ -0,0 +1,24 @@
+package foo
+
+public class Foo {
+
+    public fun blah(): Int {
+        return 5
+    }
+
+}
+
+public fun Foo.fooImp(): String {
+    return "impl" + blah()
+}
+
+public fun Foo.fooExp(): String {
+    return "expl" + this.blah()
+}
+
+fun box(): String {
+    var a = Foo()
+    if (a.fooImp() != "impl5") return "fail1: ${a.fooImp()}"
+    if (a.fooExp() != "expl5") return "fail2: ${a.fooExp()}"
+    return "OK";
+}