For as long as Review Board has existed, we've disallowed commenting on items before they're published. The reasoning here was that if you add a diff comment, replacing the diff will delete the comment (and similar for file attachments). This change updates the comment dialog to remove the `hasDraft` checks. This is replaced with a new mechanism whereby we add a `public` state to diffs and file attachments, and use that to show a warning to the user if they're commenting on something which has not yet been published. The bulk of the code changes here are just plumbing that state all the way down to the comment block models, which use it to decide what to display to the user. Testing Done: - Ran unit tests. - Created review requests with published and unpublished diffs and file attachments. Checked that adding a comment to published items worked as normal, and that the draft warnings were correctly shown for draft diffs and file attachments, as well as for interdiffs and file attachment diffs involving an unpublished tip revision.