Compile-Time support for core types

[YYF233333]

We’re about to enable C++20 for the 4.6 dev cycle. One feature I find especially valuable is C++20’s improved compile‑time computation, which means we might be able to add compile‑time support for certain core types. I’ve already made some attempts. What do you think? Which core types could benefit? Or do you have any other ideas about compile‑time computation?