Constexpr arrays in pmu_test
The new PMU constexpr _events array is working fine in the Clerk. However, its usage in pmu_test generates a compile-time error indicating an undefined reference to the _events array, even though the process is very similar (PMU::config in a new inside the inline function vs. config as an explicit call inside main). All the necessary information seems to be available at compile-time, and the constexpr vector should not be necessary during the linkage process. We still need to investigate this problem.