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

sgl-router/src/tokenizer/tests.rs

@@ -1,8 +1,9 @@
 #[cfg(test)]
-use super::*;
-#[cfg(test)]
 use std::sync::Arc;
 
+#[cfg(test)]
+use super::*;
+
 #[test]
 fn test_mock_tokenizer_encode() {
     let tokenizer = mock::MockTokenizer::new();