AstroBWT 20-50% speedup

Skips hashes with large stage 2 size. Added configurable `astrobwt-max-size` parameter, default value is 550, min 400, max 1200, optimal value ranges from 500 to 600 depending on CPU.

- Intel CPUs get 20-25% speedup
- 1st- and 2nd-gen Ryzens get 30% speedup
- 3rd-gen Ryzens get up to 50% speedup

src/backend/cpu/CpuWorker.h

@@ -70,6 +70,7 @@ private:
 
     const Algorithm m_algorithm;
     const Assembly m_assembly;
+    const int m_astrobwtMaxSize;
     const bool m_hwAES;
     const bool m_yield;
     const CnHash::AlgoVariant m_av;