Try plausibility of C++26 std::simd

[stloufra]

Description

Investigate whether C++26 std::simd can replace the existing
SIMD implementation.

The main goals are to simplify and maintain the vectorised code while checking
whether performance remains comparable/improves to the current implementation using
direct SIMD.

Tasks

• Prototype equivalent code using C++26 std::simd.
• Compare performance with the current direct implementation.
• Check numerical correctness.
• Evaluate code complexity and maintainability.

References

• C++26 std::simd — cppreference
• P1928 — std::simd