Have Batch contain Block and batch ID, ensuring eclipsed validators don't publish invalid shares

See prior commit message for more info.

With the plan for the batch sign ID to be just 5 bytes (potentially 4), this
does incur a +5 bytes cost compared to the ExternalBlock system *even in the
standard case*. The simplicity remains preferred at this time.

coordinator/src/tributary/handle.rs

@@ -443,7 +443,7 @@ pub async fn handle_application_tx<
       }
     }
 
-    Transaction::Batch(batch) => {
+    Transaction::Batch(_, batch) => {
       // Because this Batch has achieved synchrony, its batch ID should be authorized
       TributaryDb::<D>::recognize_id(txn, Zone::Batch.label(), genesis, batch);
       recognized_id(spec.set().network, genesis, RecognizedIdType::Batch, batch).await;