JS stdlib api test: various changes

- Setting -Doverwrite.output=true updates gold data
- Big packages don't get split into chunks
- Unique lines in the API are marked with /*∆*/ and diff test is removed
- Annotations on separate lines and other dump format tweaks
- Test data moved to libraries/stdlib/api/
- Minor visibility fix to Enum members

libraries/stdlib/js-ir/builtins/Enum.kt

@@ -9,11 +9,11 @@ import kotlin.js.*
 
 abstract class Enum<E : Enum<E>>(val name: String, val ordinal: Int) : Comparable<E> {
 
-    override fun compareTo(other: E) = ordinal.compareTo(other.ordinal)
+    final override fun compareTo(other: E) = ordinal.compareTo(other.ordinal)
 
-    override fun equals(other: Any?) = this === other
+    final override fun equals(other: Any?) = this === other
 
-    override fun hashCode(): Int = identityHashCode(this)
+    final override fun hashCode(): Int = identityHashCode(this)
 
     override fun toString() = name