More precise hashrate calculation

- Use only steady timestamp counters to guarantee correctness
- CPU backend: directly measure total hashrate using raw hash counters from each thread; update data more often on ARM CPUs because they're slower
- GPU backends: directly measure total hashrate too, but use interpolator with 4 second lag to fix variance from batches of hashes

Total hashrate is now measured directly (realtime for CPU, 4 seconds lag for GPU), so it might differ a bit from the sum of all thread hashrates because data points are taken at different moments in time.

Overhead is reduced a lot since it doesn't have to go through all threads to calculate max total hashrate on every timer tick (2 times a second).

src/backend/cpu/CpuWorker.cpp

@@ -218,9 +218,11 @@ void xmrig::CpuWorker<N>::start()
         alignas(16) uint64_t tempHash[8] = {};
 
         // RandomX is faster, we don't need to store stats so often
+#       ifndef XMRIG_ARM
         if (m_job.currentJob().algorithm().family() == Algorithm::RANDOM_X) {
             storeStatsMask = 63;
         }
+#       endif
 #       endif
 
         while (!Nonce::isOutdated(Nonce::CPU, m_job.sequence())) {