ChaCha AVX512 fix hotpath in XOR (#11699)

Author: SammyVimes

ydb/core/blobstorage/crypto/crypto.cpp

@@ -306,7 +306,7 @@ static void Xor(void* destination, const void* a, const void* b, ui32 size) {
         ++srcB;
     }
 #else
-    if (NX86::HaveAVX512F()) {
+    if (TStreamCypher::HasAVX512) {
         XorAVX512(destination, a, b, size);
     } else {
         ui8 *dst = (ui8*)destination;

ydb/core/blobstorage/crypto/crypto.h

@@ -98,12 +98,14 @@ using TT1ha0Avx2Hasher = TT1ha0HasherBase<ET1haFunc::T1HA0_AVX2>;
 ////////////////////////////////////////////////////////////////////////////
 
 class TStreamCypher {
+public:
+    static const bool HasAVX512;
+private:
     alignas(16) ui8 Leftover[BLOCK_BYTES];
     alignas(16) ui64 Key[4];
     alignas(16) i64 Nonce;
     std::unique_ptr<std::variant<ChaChaVec, ChaCha512>> Cypher;
     ui32 UnusedBytes;
-    static const bool HasAVX512;
 public:
     TStreamCypher();
     void SetKey(const ui64 &key);