Clean up imports, formatting and tests.

Bug: n/a
Test: atest libapkverify.test libapkverify.integration_test
Change-Id: I39686d17927741297aa3feb02ed6043ee770933b
diff --git a/apkverify/src/bytes_ext.rs b/apkverify/src/bytes_ext.rs
index 1b8d6b6..22a3085 100644
--- a/apkverify/src/bytes_ext.rs
+++ b/apkverify/src/bytes_ext.rs
@@ -98,7 +98,9 @@
 
 #[cfg(test)]
 mod tests {
+    use super::*;
     use bytes::{BufMut, BytesMut};
+
     #[test]
     fn test_read_length_prefixed_slice() {
         let data = b"hello world";
@@ -106,7 +108,7 @@
         b.put_u32_le(data.len() as u32);
         b.put_slice(data);
         let mut slice = b.freeze();
-        let res = super::read_length_prefixed_slice(&mut slice);
+        let res = read_length_prefixed_slice(&mut slice);
         assert!(res.is_ok());
         assert_eq!(data, res.ok().unwrap().as_ref());
     }