[libc] [llvm] [libc][NFC] Remove __support/bit.h and use __support/CPP/bit.h instead (PR #73939)

[Schrodinger ZHU Yifan via llvm-commits]

SchrodingerZhu wrote:

I am getting 500 errors from the GitHub server if I open the review page, but https://www.githubstatus.com/ does not show any incident. Will take a look later.

https://github.com/llvm/llvm-project/pull/73939