[2025-02 LWG Motion 13] P2933R4 Extend ⟨bit⟩ header function with overloads for std::simd

[jensmaurer]

P2933R4 (Extend ⟨bit⟩ header function with overloads for std::simd)

[mattkretz]

I'm working on this now. Note that #7671 adds the same exposition-only concept. Therefore I suggest we let #7671 depend on this one.