bench: explicitly make all current benchmarks "high" priority

no-functional changes. Only have set the priority level explicitly
on every BENCHMARK macro call.

src/bench/checkqueue.cpp

@@ -70,4 +70,4 @@ static void CCheckQueueSpeedPrevectorJob(benchmark::Bench& bench)
     queue.StopWorkerThreads();
     ECC_Stop();
 }
-BENCHMARK(CCheckQueueSpeedPrevectorJob);
+BENCHMARK(CCheckQueueSpeedPrevectorJob, benchmark::PriorityLevel::HIGH);