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

js/js.translator/testData/box/closure/implicitGenericReceiverInExtensionInLocalClass.kt

@@ -0,0 +1,17 @@
+package foo
+
+class A {
+    fun test() = 23
+}
+
+fun <T : A> T.foo(): Int {
+    class B {
+        fun foo() = test()
+    }
+    return B().foo()
+}
+
+fun box(): String {
+    assertEquals(23, A().foo())
+    return "OK"
+}