Compilation errors in big5_hkscs.hpp and gbk_or_gb18030.hpp on macOS with Apple Clang

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Several compilation errors occur when using Big5 and GB18030 encodings on macOS with Apple Clang 17. The issues are:

1. big5_hkscs.hpp: Misplaced parenthesis in std::addressof call and invalid constexpr lambda
2. gbk_or_gb18030.hpp: Type mismatch in replacement_code_points() function

Minimal reproduction code:

#include <string>
#include <span>
#include <ztd/text.hpp>

int main() {
    std::string big5_input = "\xa4\xa4";  // Chinese character for "middle"
    std::span<const char> input(big5_input.data(), big5_input.size());

    // This fails to compile
    auto result = ztd::text::transcode(input, ztd::text::big5_hkscs, ztd::text::compat_utf8,
                                       ztd::text::replacement_handler);
    return 0;
}

My fix here: 23459c9