Add caution box to Labels page for deleting labels
Problem to solve
Deleting labels is a destructive action that does not have an undo, and doesn't leave any trace of the label in the system after removal. We should let the user know more about the delete action than just the warning/confirmation that happens in the application at the time of deletion.
Add a caution alert to the Labels page where label deletion is mentioned, to indicate that label removal is permanent (no restoration capability), and that there will be no indication of the removed label within the system (including no references in issue/MR changelogs). You'll want to confirm that last part, but that seems to be GitLab's behavior, and as such, we should call that out before people click the Delete link and get the final confirmation.