feat: replace woort_utf8 with woolang wo_utf8 implementation
- Replace C-style woort_utf8.h/c with C++ woort_utf8.hpp/cpp
- Port wo_utf8 implementation from woolang project
- Provides enhanced UTF-8/UTF-16/UTF-32 conversion utilities
- Added string encoding/decoding support (u8enstring/u8destring)
- Better surrogate pair handling for UTF-16