(CpuId) Add AVX512 VNNI feature detection

Adds AVX512 VNNI to NX86 CPU feature detection and cached flags, plus the corresponding CpuId unit-test hook. This PR is limited to `util/system/` changes.

Verification:
- `ya make -tt util/system/ut -F TestCpuId`
commit_hash:be9c9e83f684838f3e5d9e390636c2bd5e1e0342

Author: mirali777

util/system/cpu_id.cpp

@@ -231,6 +231,10 @@ bool NX86::HaveAVX512VL() noexcept {
     return HaveAVX512F() && ((TX86CpuInfo(0x7, 0).EBX >> 31) & 1u);
 }
 
+bool NX86::HaveAVX512VNNI() noexcept {
+    return HaveAVX512F() && ((TX86CpuInfo(0x7, 0).ECX >> 11) & 1u);
+}
+
 bool NX86::HavePREFETCHWT1() noexcept {
     return TX86CpuInfo(0x0).EAX >= 0x7 && ((TX86CpuInfo(0x7, 0).ECX >> 0) & 1u);
 }

util/system/cpu_id.h

@@ -28,6 +28,7 @@
     F(AVX512CD)               \
     F(AVX512BW)               \
     F(AVX512VL)               \
+    F(AVX512VNNI)             \
     F(AVX512VBMI)             \
     F(PREFETCHWT1)            \
     F(SHA)                    \
@@ -58,6 +59,7 @@
     F(AVX512CD)                                      \
     F(AVX512BW)                                      \
     F(AVX512VL)                                      \
+    F(AVX512VNNI)                                    \
     F(AVX512VBMI)                                    \
     F(PREFETCHWT1)                                   \
     F(SHA)                                           \