feat: ShuffleState and QuarterRound AVX2 and SSE3 and ARM AdvSIMD

[daviddesmet]

First take on .NET Hardware Intrinsics:

• Support AVX2 and SSE3 in ChaCha20Base.ShuffleState
• Support AVX2 and SSE3 in ChaCha20Base.QuarterRound

Implemented proper SSE2 and AdvSIMD optimizations for Poly1305:

• ComputeMacSse2 - Uses SSE2 Vector128 intrinsics for:
  • SIMD loads for key and data blocks
  • SIMD store for the final 16-byte tag output
  • The polynomial multiplication remains scalar due to data dependencies inherent to Poly1305's design
• ComputeMacAdvSimd - Uses ARM AdvSIMD Vector128 intrinsics with the same optimization pattern for ARM64 platforms (like macOS)
• Updated ComputeMac dispatch to check for SSE2 and AdvSIMD support after AVX2

Pending:

• Support AVX2 and SSE3 and ARM AdvSIMD in Salsa20Base

[Copilot]

Pull Request Overview

This PR introduces .NET Hardware Intrinsics support for optimizing ChaCha20 cryptographic operations with AVX2, SSE3, and ARM AdvSIMD instruction sets. The implementation provides SIMD-accelerated versions of core ChaCha20 operations (ShuffleState and QuarterRound) while maintaining backward compatibility with scalar implementations.

Key changes:

• Added hardware intrinsics support for ChaCha20 core operations with AVX2, SSE3, and ARM AdvSIMD
• Enhanced build and test infrastructure to validate intrinsics across different platforms
• Updated dependencies and improved code style consistency across benchmark files

Reviewed Changes

Copilot reviewed 25 out of 25 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
src/NaCl.Core/Base/ChaCha20Base.cs	Core SIMD implementation with hardware intrinsics for ShuffleState and QuarterRound operations
src/NaCl.Core/Internal/BitUtils.cs	Added SIMD-optimized rotation utilities for Vector128/256 operations
test/NaCl.Core.Benchmarks/ChaCha20IntrinsicsBenchmark.cs	New benchmark class specifically for testing hardware intrinsics performance
build.cake	Enhanced build script with platform-specific intrinsics testing
test/NaCl.Core.Benchmarks/*.cs	Code style improvements and field naming consistency
src/NaCl.Core/Internal/ArrayUtils.cs	Fixed method naming inconsistency
test/NaCl.Core.Tests/*.cs	Updated test vectors URL and method visibility

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[codecov]

Codecov Report

❌ Patch coverage is 98.03408% with 15 lines in your changes missing coverage. Please review.
✅ Project coverage is 90.42%. Comparing base (b01b811) to head (d26a16e).
⚠️ Report is 2 commits behind head on master.

Files with missing lines	Patch %	Lines
src/NaCl.Core/Poly1305.cs	96.95%	9 Missing ⚠️
src/NaCl.Core/Base/ChaCha20Base.cs	97.87%	2 Missing ⚠️
src/NaCl.Core/Base/Salsa20Base.cs	98.54%	2 Missing ⚠️
src/NaCl.Core/Base/Snuffle.cs	95.74%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #159      +/-   ##
==========================================
- Coverage   99.78%   90.42%   -9.36%     
==========================================
  Files          14       14              
  Lines         455     1201     +746     
  Branches       57      128      +71     
==========================================
+ Hits          454     1086     +632     
- Misses          1      115     +114     

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