fix: crash ExEx task when the ExEx future returns (#7633)

Co-authored-by: Oliver Nordbjerg <onbjerg@users.noreply.github.com>

crates/node-builder/src/builder.rs

@@ -627,7 +627,10 @@ where
                 // spawn it as a crit task
                 executor.spawn_critical("exex", async move {
                     info!(target: "reth::cli", id, "ExEx started");
-                    exex.await.unwrap_or_else(|_| panic!("exex {} crashed", id))
+                    match exex.await {
+                        Ok(_) => panic!("ExEx {id} finished. ExEx's should run indefinitely"),
+                        Err(err) => panic!("ExEx {id} crashed: {err}"),
+                    }
                 });
             });
         }