[clang] [clang]Implement the c23 stdc bit builtins (PR #185978)

[Erich Keane via cfe-commits]

https://github.com/erichkeane commented:

Typically we don't bother to implement these unless libc starts using these, or needs them.  Making builtins for these functions without the library needs them is kinda silly.

DO we have a request for these coming from the libc maintainers?

https://github.com/llvm/llvm-project/pull/185978