Adjust preview API error reporting based on new JavaSE API

[Bug 549809 ](https://bugs.eclipse.org/bugs/show_bug.cgi?id=549809) added support for reporting usage of preview system APIs. But since then, the @PreviewFeature API has undergone significant changes that is affecting the ECJ error reporting. Notably, tags like essentialAPIs have been removed and new taxonomy has been introduced. This is documented in [JEP 12: Preview Features](https://openjdk.java.net/jeps/12)

Our error reporting should be adjusted to reflect this whenever these get finalized.