Implement P0533R9 (C++23 `constexpr` `<cmath>`) for Clang and EDG

[StephanTLavavej]

Followup to #2530.

We need to implement WG21-P0533R9 "constexpr For <cmath> And <cstdlib>" for Clang and EDG.

[frederick-vs-ja]

For Clang this is also tracked in LLVM-139885.