use std::numbers when transitioning to c++20

[PrometheusPi]

C++ 20 introduces the library numbers https://en.cppreference.com/w/cpp/header/numbers. What do you think of using it to replace some hard coded values in https://github.com/ComputationalRadiationPhysics/picongpu/blob/dev/include/picongpu/param/physicalConstants.param (Sadly, it does not introduce physics constants.)

[BrianMarre]

sounds like a great idea, especially the sqrt_3 and pi will be really helpful