[NFC][libc++][format] Use ranges in the output.

[Mordante]

Summary

This should avoid some copies of the output iterator.

libcxx/include/__format/formatter_output.h

 // -*- C++ -*-
 //===----------------------------------------------------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
 #ifndef _LIBCPP___FORMAT_FORMATTER_OUTPUT_H
 #define _LIBCPP___FORMAT_FORMATTER_OUTPUT_H
 
-#include <__algorithm/copy.h>
-#include <__algorithm/copy_n.h>
-#include <__algorithm/fill_n.h>
-#include <__algorithm/transform.h>
+#include <__algorithm/ranges_copy.h>
+#include <__algorithm/ranges_fill_n.h>
+#include <__algorithm/ranges_transform.h>
 #include <__concepts/same_as.h>
 #include <__config>
 #include <__format/buffer.h>
 #include <__format/formatter.h>
 #include <__format/parser_std_format_spec.h>
 #include <__format/unicode.h>
 #include <__iterator/back_insert_iterator.h>
 #include <__utility/move.h>

 /// This uses a "mass output function" of __format::__output_buffer when possible.
 template <__formatter::__char_type _CharT, __formatter::__char_type _OutCharT = _CharT>
 _LIBCPP_HIDE_FROM_ABI auto __copy(basic_string_view<_CharT> __str, output_iterator<const _OutCharT&> auto __out_it)
     -> decltype(__out_it) {
   if constexpr (_VSTD::same_as<decltype(__out_it), _VSTD::back_insert_iterator<__format::__output_buffer<_OutCharT>>>) {
     __out_it.__get_container()->__copy(__str);
     return __out_it;
   } else {
-    return std::copy_n(__str.data(), __str.size(), _VSTD::move(__out_it));
+    return std::ranges::copy(__str, _VSTD::move(__out_it)).out;
   }
 }
 
 template <__formatter::__char_type _CharT, __formatter::__char_type _OutCharT = _CharT>
 _LIBCPP_HIDE_FROM_ABI auto
 __copy(const _CharT* __first, const _CharT* __last, output_iterator<const _OutCharT&> auto __out_it)
     -> decltype(__out_it) {
   return __formatter::__copy(basic_string_view{__first, __last}, _VSTD::move(__out_it));

 __transform(const _CharT* __first,
             const _CharT* __last,
             output_iterator<const _OutCharT&> auto __out_it,
             _UnaryOperation __operation) -> decltype(__out_it) {
   if constexpr (_VSTD::same_as<decltype(__out_it), _VSTD::back_insert_iterator<__format::__output_buffer<_OutCharT>>>) {
     __out_it.__get_container()->__transform(__first, __last, _VSTD::move(__operation));
     return __out_it;
   } else {
-    return std::transform(__first, __last, _VSTD::move(__out_it), __operation);
+    return std::ranges::transform(__first, __last, _VSTD::move(__out_it), __operation).out;
   }
 }
 
 /// Fill wrapper.
 ///
 /// This uses a "mass output function" of __format::__output_buffer when possible.
 template <__formatter::__char_type _CharT, output_iterator<const _CharT&> _OutIt>
 _LIBCPP_HIDE_FROM_ABI _OutIt __fill(_OutIt __out_it, size_t __n, _CharT __value) {
   if constexpr (_VSTD::same_as<decltype(__out_it), _VSTD::back_insert_iterator<__format::__output_buffer<_CharT>>>) {
     __out_it.__get_container()->__fill(__n, __value);
     return __out_it;
   } else {
-    return std::fill_n(_VSTD::move(__out_it), __n, __value);
+    return std::ranges::fill_n(_VSTD::move(__out_it), __n, __value);
   }
 }
 
 template <class _OutIt, class _CharT>
 _LIBCPP_HIDE_FROM_ABI _OutIt __write_using_decimal_separators(_OutIt __out_it, const char* __begin, const char* __first,
                                                               const char* __last, string&& __grouping, _CharT __sep,
                                                               __format_spec::__parsed_specifications<_CharT> __specs) {
   int __size = (__first - __begin) +    // [sign][prefix]