EZArgs.h conceptualized

1. [Change] bux::C_EZArgs methods conceptualized.
2. [Change][Incompatible] bux::C_ErrorOrIndex knows the difference between error and help text.
3. [Change] Argument dirs of bux::search_dirs() is now typed as std::ranges::forward_range instead of in-house bux::ConstPathList
4. [Change] const std::string & is somtimes more efficient than std::string_view
5. [Change] Methods of bux::C_EZArgs tuned for uint tests to pass. But the changes are also healthier and more tolerable in the long run.
6. [New] RAW_LOGIC_ERROR(), RAW_RUNTIME_ERROR() with no source trace, just the formatted message.

p.s. This release id not for clang, which is lack of C++20 P0634R3 feature.