RustCrypto utils

• CVE-2026-50185 Low 2.0 RustCrypto Cmov/CmovEq on aarch64 can produce wrong results if high-bits of registers are set 0.2%
• CVE-2026-23519 High 8.9 RustCrypto cmov: thumbv6m-none-eabi compiler emits non-constant time assembly when using cmovnz 0.6%