rose edit: revert page now reverts errors

This change allows the "Revert page to last saved state" action in `rose edit` to revert errors and warnings. This is not necessary for the dynamic error checking such as for the `type`, `range`, `values`... metadata, but it is necessary for custom errors from macros, and non-dynamic error sources such as `fail-if`/`warn-if`.

This change can be tested using the fail-if condition in the `demo/rose-config-edit/training/app/cooking` app.

@matthewrmshin, please review.