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/lockedpool.cpp

@@ -39,4 +39,4 @@ static void BenchLockedPool(benchmark::Bench& bench)
     addr.clear();
 }
 
-BENCHMARK(BenchLockedPool);
+BENCHMARK(BenchLockedPool, benchmark::PriorityLevel::HIGH);