P3364 R0 Remove Deprecated u8path overloads From C++26

[wg21bot]

P3364R0 Remove Deprecated u8path overloads From C++26 (Alisdair Meredith)

[tahonermann]

SG16 reviewed P3364R0 during its 2024-09-11 meeting. The following polls were taken:

• Poll 3: P2319R0: In the long term we want to remove std::filesystem::u8path
  (with the implication that, if we don't, that we will undeprecate it).
  • Attendees: 10

    SF	F	N	A	SA
    4	2	0	0	2

  • Consensus in favor.

Concerns linger regarding the performance implications of migrating existing code from std::filesystem::u8path() to std::filesystem::path constructors. It would be helpful to have a performance analysis that compares use of u8path() with a replacement function implemented like the following:

std::filesystem::path u8path_from_transform_view(const std::string &s) {
  auto u8view = std::ranges::views::transform(s, [](char c) -> char8_t { return c; });
  return std::filesystem::path{u8view.begin(), u8view.end()};
}