add graceful shutdown signal to coordinator and all background tasks

hive-c0re/src/stats_vacuum.rs

@@ -22,11 +22,17 @@ const KEEP_SECS: i64 = 90 * 24 * 3600;
 /// the vacuum SQL against its turn-stats.sqlite if present. Errors
 /// are logged but don't tear the loop down.
 pub fn spawn(coord: Arc<Coordinator>) {
+    let mut shutdown = coord.shutdown_rx();
     tokio::spawn(async move {
         loop {
             sweep_once();
-            let _ = &coord;
-            tokio::time::sleep(VACUUM_INTERVAL).await;
+            tokio::select! {
+                _ = tokio::time::sleep(VACUUM_INTERVAL) => {}
+                _ = shutdown.changed() => {
+                    tracing::info!("stats vacuum: shutdown signal received");
+                    break;
+                }
+            }
         }
     });
 }