One feature that was missing from the new banner that was present in the old was a confirmation dialog when discarding a draft review. Additionally, we didn't have any kind of confirmation step when discarding review request drafts. This change implements both of those in the new UI. Testing Done: Discarded review request drafts and review drafts. Saw the confirmation dialog, which canceled the operation through either the escape key or clicking the cancel button, and proceeded when clicking the discard button.