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/api/js/kotlin.io.kt

@@ -0,0 +1,5 @@
+public fun print(message: kotlin.Any?): kotlin.Unit
+
+public fun println(): kotlin.Unit
+
+public fun println(message: kotlin.Any?): kotlin.Unit