misc: Further improve imports styling

By introducing `imports_granularity="Module"` format strategy,
effectively groups imports from the same module into one line or block,
improving maintainability and readability.

Signed-off-by: Ruoqing He <heruoqing@iscas.ac.cn>

net_util/src/mac.rs

@@ -5,9 +5,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the THIRD-PARTY file.
 
-use std::fmt;
-use std::io;
 use std::str::FromStr;
+use std::{fmt, io};
 
 use serde::de::{Deserialize, Deserializer, Error};
 use serde::ser::{Serialize, Serializer};