Test the rest of the worker protocol serializers

Part of the `BuildResult` test is commented out because we have caught a
roundtrip bug! A future PR will fix the bug and uncomment that test.

src/libstore/build-result.hh

@@ -3,6 +3,7 @@
 
 #include "realisation.hh"
 #include "derived-path.hh"
+#include "comparator.hh"
 
 #include <string>
 #include <chrono>
@@ -100,6 +101,8 @@ struct BuildResult
      */
     std::optional<std::chrono::microseconds> cpuUser, cpuSystem;
 
+    DECLARE_CMP(BuildResult);
+
     bool success()
     {
         return status == Built || status == Substituted || status == AlreadyValid || status == ResolvesToAlreadyValid;