QMetaTypeForType::name: msvc constexpr limitation

i'm not sure if there's an easy way around this: i'm using some very long `std::variant`s as signal arguments. the types are registered to the meta type system, but when compiling
```static constexpr decltype(typenameHelper<S>()) name = typenameHelper<S>();```, msvc bails out with "error C2131: expression did not evaluate to a constant"

include\QtCore/qmetatype.h(1798): note: failure was caused by evaluation exceeding step limit of 1048576 (/constexpr:steps<NUMBER>)

while i've been able to work around by increasing the `/constexpr:steps` count, i wonder if there's something that can be done in the constexpr computation