visit_format_arg forces formatting of 'long double'

[j8asic]

The visit_format_arg function in core.h always tries to format long_double_type, which creates compile errors when long double math is disabled (sometimes we have FMT_USE_FLOAT128=0 because there are no implementations of those math functions e.g. for CUDA under libc++). So this case should be treated similar like for int128_type case is treated using FMT_USE_INT128. I.e. FMT_USE_FLOAT128 should be checked and taken into account.

[tt4g]

The sources saved in the directory include/spdlog/fmt/bundled/ are from the fmt library, please move the issue to the fmt project.

[j8asic]

Thanks I completely missed. I tried reporting it previously here https://github.com/fmtlib/fmt/issues/3106 , now I added more description there