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.browser.kt

@@ -0,0 +1,7 @@
+public external val document: org.w3c.dom.Document { get; }
+
+public external val localStorage: org.w3c.dom.Storage { get; }
+
+public external val sessionStorage: org.w3c.dom.Storage { get; }
+
+public external val window: org.w3c.dom.Window { get; }