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

[Hristo Hristov via cfe-commits]

Zingam wrote:

I'm relanding this and I'll keep eyes on it here: https://ci.chromium.org/ui/p/fuchsia/builders/toolchain.ci/clang-windows-x64

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