Merge "Add missing libc++ includes" into main

#pragma once

#include <functional>

#include <optional>

#include <ostream>

#include <string>

// ETA for this blocker is 2023-10-27~2023-11-10.

// Also, remember to remove fmtlib's format.cc from trusty makefiles.

#if __has_include(<format>)

#if __has_include(<format>) && !defined(_LIBCPP_HAS_NO_INCOMPLETE_FORMAT)

#include <format>

#else

#include <fmt/format.h>