[llvm] [clang] [libcxx] Reapply "[libc++][streams] P1759R6: Native handles and file streams" (PR #77190)

[via cfe-commits]

https://github.com/zeroomega commented:

I test run it with C++26 on Windows, it clears the test failures happened in the original PR.

https://github.com/llvm/llvm-project/pull/77190