[libc][wctype] Move classification lookup tables to a cpp file (#174993)
#170525
Previously, lookup tables were defined in a header so that they can be
constexpr, but this lead to each translation unit having it's own copy,
bloating the library size. Looking at current usages of wctype
functions, they are always used at runtime, so there's no benefit of
having them constexpr, so I'm moving them to a cpp file, so that there's
only a single copy in the library.