Clean up conformance tests warnings and formatting.

PiperOrigin-RevId: 574304654
diff --git a/conformance/conformance_test.h b/conformance/conformance_test.h
index 0e3fb70..bdc7a69 100644
--- a/conformance/conformance_test.h
+++ b/conformance/conformance_test.h
@@ -14,13 +14,15 @@
 #ifndef CONFORMANCE_CONFORMANCE_TEST_H
 #define CONFORMANCE_CONFORMANCE_TEST_H
 
-#include <functional>
+#include <cstddef>
+#include <memory>
 #include <string>
 #include <vector>
 
 #include "google/protobuf/util/type_resolver.h"
 #include "absl/container/btree_set.h"
 #include "absl/container/flat_hash_set.h"
+#include "absl/strings/string_view.h"
 #include "conformance/conformance.pb.h"
 #include "google/protobuf/descriptor.h"
 #include "google/protobuf/wire_format_lite.h"
@@ -204,7 +206,7 @@
       return request_;
     }
 
-    const ConformanceLevel GetLevel() const { return level_; }
+    ConformanceLevel GetLevel() const { return level_; }
 
     std::string ConformanceLevelToString(ConformanceLevel level) const;
 
@@ -245,9 +247,9 @@
                       bool need_report_success, bool require_same_wire_format);
 
   void TruncateDebugPayload(std::string* payload);
-  const conformance::ConformanceRequest TruncateRequest(
+  conformance::ConformanceRequest TruncateRequest(
       const conformance::ConformanceRequest& request);
-  const conformance::ConformanceResponse TruncateResponse(
+  conformance::ConformanceResponse TruncateResponse(
       const conformance::ConformanceResponse& response);
 
   void ReportSuccess(const std::string& test_name);