AVX2 optimized code for AstroBWT

Added "astrobwt-avx2" parameter in config.json, it's turned off ("false") by default.

4-5% speedup on CPUs with proper AVX2 support (AMD Ryzen starting with Zen2, Intel Core starting with Haswell).

There will be no speedup on the following CPUs:

- Intel Pentium/Celeron don't support AVX2
- AMD Zen/Zen+ have only half-speed AVX

GCC compiled version is faster without AVX2, MSVC compiled version is faster with AVX2

src/backend/cpu/CpuWorker.cpp

@@ -81,6 +81,7 @@ xmrig::CpuWorker<N>::CpuWorker(size_t id, const CpuLaunchData &data) :
     m_yield(data.yield),
     m_av(data.av()),
     m_astrobwtMaxSize(data.astrobwtMaxSize * 1000),
+    m_astrobwtAVX2(data.astrobwtAVX2),
     m_miner(data.miner),
     m_ctx()
 {
@@ -262,7 +263,7 @@ void xmrig::CpuWorker<N>::start()
             {
 #               ifdef XMRIG_ALGO_ASTROBWT
                 if (job.algorithm().family() == Algorithm::ASTROBWT) {
-                    if (!astrobwt::astrobwt_dero(m_job.blob(), job.size(), m_ctx[0]->memory, m_hash, m_astrobwtMaxSize))
+                    if (!astrobwt::astrobwt_dero(m_job.blob(), job.size(), m_ctx[0]->memory, m_hash, m_astrobwtMaxSize, m_astrobwtAVX2))
                         valid = false;
                 }
                 else