[router] Add rustfmt and set group imports by default (#11732)

sgl-router/src/core/token_bucket.rs

@@ -1,5 +1,8 @@
-use std::sync::Arc;
-use std::time::{Duration, Instant};
+use std::{
+    sync::Arc,
+    time::{Duration, Instant},
+};
+
 use tokio::sync::{Mutex, Notify};
 use tracing::{debug, trace};