WIP: Annotate & IOU-test j.u.List default methods

This PR builds upon merged PR scala-native#1937 by adding the JavaDefaultMethod
annotation to the trait

IOU: The discerning reader will notice that there is no ListTest.scala
     in this WIP.

     Before this PR can move out of WIP state the corresponding
     Scala.js ListTest.scala should be ported. Currently ScalaNative
     has no ListTest.

     Scala.js ListTest has a number of prerequisites, few of which
     are currently ported (such as TestMainBase).  I believe
     porting those items in a series of separate PRs. Tedious, but
     it will leave a better audit trail.

See Issue scala-native#1972 for background & discussion of JavaDefaultMethod
annotation.

This PR is WIP because it will fail to build until after PR scala-native#1997
is merged and this PR re-based upon it.

javalib/src/main/scala/java/util/List.scala

@@ -1,21 +1,51 @@
+// Ported from Scala.js commit: ad7d82f dated: 2020-10-05
+
 package java.util
 
+import java.util.function.UnaryOperator
+
+import scala.scalanative.annotation.JavaDefaultMethod
+
 trait List[E] extends Collection[E] {
+  @JavaDefaultMethod
+  def replaceAll(operator: UnaryOperator[E]): Unit = {
+    val iter = listIterator()
+    while (iter.hasNext())
+      iter.set(operator.apply(iter.next()))
+  }
+
+  @JavaDefaultMethod
+  def sort(c: Comparator[_ >: E]): Unit = {
+    val arrayBuf = toArray()
+    Arrays.sort[AnyRef with E](arrayBuf.asInstanceOf[Array[AnyRef with E]], c)
+
+    val len = arrayBuf.length
+
+    if (this.isInstanceOf[RandomAccess]) {
+      var i = 0
+      while (i != len) {
+        set(i, arrayBuf(i).asInstanceOf[E])
+        i += 1
+      }
+    } else {
+      var i    = 0
+      val iter = listIterator()
+      while (i != len) {
+        iter.next()
+        iter.set(arrayBuf(i).asInstanceOf[E])
+        i += 1
+      }
+    }
+  }
+
   def get(index: Int): E
   def set(index: Int, element: E): E
-  def add(element: E): Boolean
   def add(index: Int, element: E): Unit
   def remove(index: Int): E
   def indexOf(o: Any): Int
   def lastIndexOf(o: Any): Int
   def listIterator(): ListIterator[E]
   def listIterator(index: Int): ListIterator[E]
   def subList(fromIndex: Int, toIndex: Int): List[E]
-  def addAll(c: Collection[_ <: E]): Boolean
   def addAll(index: Int, c: Collection[_ <: E]): Boolean
-  def clear(): Unit
-  def isEmpty(): Boolean
-  def iterator(): Iterator[E]
-  def contains(o: Any): Boolean
-  def size(): Int
 }