* Add std::string_view overloads for std::from_chars
std::from_chars floating point support is still pour, so we provide some
fall backs. These fall backs currently lack error handling.
(since GCC 11 and MSVC 2019 16.4 FP support is added, clang with libc++
still doesn't support FP)
GCC's floating point support is still rather pour (performance) and
probably shouldn't be used, but we have support to if people want to
now.
Probably need more test cases ...
* Fix issue with std::chars_format define lacking
My test case for lacking FP support was clang with libc++ which defined
this enum anyways.
