JS lib: added hasNext to Kotlin.ListIterator and fixed next.

#KT-6506 Fixed

Additionally made abstract AbstractList::get and AbstractCollection::size.

js/js.translator/testData/java/abstractList/cases/iterator.kt

@@ -0,0 +1,32 @@
+package foo
+
+import java.util.AbstractList
+
+class MyList<T>(vararg val data: T) : AbstractList<T>() {
+    override fun get(index: Int) = data[index]
+    override fun size() = data.size()
+}
+
+fun test<T>(expected: String, list: List<T>) {
+    var s = ""
+    for (e in list) {
+        s += "$e,"
+    }
+    assertEquals(expected, s)
+
+    val it = list.iterator()
+    s = ""
+    while (it.hasNext()) {
+        val e = it.next()
+        s += "$e,"
+    }
+    assertEquals(expected, s)
+}
+
+fun box(): String {
+
+    test("32,12,23,444,", MyList(32, 12, 23, 444))
+    test("", MyList<Any>())
+
+    return "OK"
+}