Allow opting out of workqueue tracking with a label

This allows reviewers to add a `S-no-work-capacity-tracking` label to a PR. When this label is present, the PR will not count towards the review queue capacity of a reviewer assigned to that PR.

Author: Kobzol

src/handlers/pr_tracking.rs

@@ -324,13 +324,17 @@ fn waits_for_a_review(
     let is_rollup = labels.iter().any(|l| l.name == "rollup");
     let is_waiting_for_reviewer = labels.iter().any(|l| l.name == "S-waiting-on-review");
     let is_assigned_to_author = assignees.contains(author);
+    let has_capacity_tracking_opt_out = labels
+        .iter()
+        .any(|l| l.name == "S-no-work-capacity-tracking");
 
     is_open
         && !is_draft
         && !is_blocked
         && !is_rollup
         && is_waiting_for_reviewer
         && !is_assigned_to_author
+        && !has_capacity_tracking_opt_out
 }
 
 #[cfg(test)]