demotes WeightedShuffle failures to error metrics (#24079)

Since call-sites are calling unwrap anyways, panicking seems too punitive
for our use cases.

core/src/cluster_nodes.rs

@@ -326,7 +326,7 @@ pub fn new_cluster_nodes<T: 'static>(
         .collect();
     let broadcast = TypeId::of::<T>() == TypeId::of::<BroadcastStage>();
     let stakes: Vec<u64> = nodes.iter().map(|node| node.stake).collect();
-    let mut weighted_shuffle = WeightedShuffle::new(&stakes).unwrap();
+    let mut weighted_shuffle = WeightedShuffle::new("cluster-nodes", &stakes);
     if broadcast {
         weighted_shuffle.remove_index(index[&self_pubkey]);
     }