[libc][math] Refactor sincosf implementation to header only (#177523) Part of #147386 in preparation for: https://discourse.llvm.org/t/rfc-make-clang-builtin-math-functions-constexpr-with-llvm-libc-to-support-c-23-constexpr-math-functions/86450 Closes #177640 GitOrigin-RevId: a17bc05818264a1eef3796cc5b0856a3cd3e808b