Soft-leader election mechanism for cc based on observed cluster state

Fixes #2238

Author: muhamadazmy

crates/admin/src/cluster_controller/cluster_state_refresher.rs

@@ -235,4 +235,8 @@ impl ClusterStateWatcher {
             .map_err(|_| ShutdownError)?;
         Ok(Arc::clone(&self.cluster_state_watcher.borrow_and_update()))
     }
+
+    pub fn current(&self) -> Arc<ClusterState> {
+        Arc::clone(&self.cluster_state_watcher.borrow())
+    }
 }