Import macros exclusively through serde_derive in test suite

This makes it easier to execute tests against the precompiled serde_derive.

test_suite/tests/test_annotations.rs

@@ -10,8 +10,9 @@
     clippy::uninlined_format_args,
 )]
 
-use serde::de::{self, IgnoredAny, MapAccess, Unexpected, Visitor};
-use serde::{Deserialize, Deserializer, Serialize, Serializer};
+use serde::de::{self, Deserialize, Deserializer, IgnoredAny, MapAccess, Unexpected, Visitor};
+use serde::ser::{Serialize, Serializer};
+use serde_derive::{Deserialize, Serialize};
 
 use std::collections::{BTreeMap, HashMap};
 use std::convert::TryFrom;