review classifier: a setting makes the PR review list only the failed rules

failures_only (off by default, also for a stored document without it) makes the
review the classifier posts on a PR list just the rows that failed their rule,
or say that no check failed on an approval. A review with no clean verdict and
a try-out keep every row. The classifier settings form gets a checkbox for it.

swarm-controller/src/review_classifier.rs

@@ -1053,6 +1053,7 @@ pub(crate) mod tests {
                 effort: Some(Effort::High),
                 max_concurrent_reviews: 2,
                 max_classifications: 10,
+                failures_only: false,
                 runtime: settings::RuntimeKind::Acp,
                 acp: Some(acp.clone()),
             },