[libc++][print] Renames __use_unicode. (#76290)

This is addresses a review comment in #73262.

Author: mordante

libcxx/include/ostream

@@ -1137,7 +1137,7 @@ template <class... _Args>
 _LIBCPP_AVAILABILITY_PRINT _LIBCPP_HIDE_FROM_ABI void
 print(ostream& __os, format_string<_Args...> __fmt, _Args&&... __args) {
 #  ifndef _LIBCPP_HAS_NO_UNICODE
-  if constexpr (__print::__use_unicode)
+  if constexpr (__print::__use_unicode_execution_charset)
     std::__vprint_unicode(__os, __fmt.get(), std::make_format_args(__args...), false);
   else
     std::__vprint_nonunicode(__os, __fmt.get(), std::make_format_args(__args...), false);
@@ -1153,7 +1153,7 @@ println(ostream& __os, format_string<_Args...> __fmt, _Args&&... __args) {
   // Note the wording in the Standard is inefficient. The output of
   // std::format is a std::string which is then copied. This solution
   // just appends a newline at the end of the output.
-  if constexpr (__print::__use_unicode)
+  if constexpr (__print::__use_unicode_execution_charset)
     std::__vprint_unicode(__os, __fmt.get(), std::make_format_args(__args...), true);
   else
     std::__vprint_nonunicode(__os, __fmt.get(), std::make_format_args(__args...), true);

libcxx/include/print

@@ -192,13 +192,13 @@ namespace __print {
 //
 
 #  ifdef _LIBCPP_HAS_NO_UNICODE
-inline constexpr bool __use_unicode = false;
+inline constexpr bool __use_unicode_execution_charset = false;
 #  elif defined(_MSVC_EXECUTION_CHARACTER_SET)
 // This is the same test MSVC STL uses in their implementation of <print>
 // See: https://learn.microsoft.com/en-us/windows/win32/intl/code-page-identifiers
-inline constexpr bool __use_unicode = _MSVC_EXECUTION_CHARACTER_SET == 65001;
+inline constexpr bool __use_unicode_execution_charset = _MSVC_EXECUTION_CHARACTER_SET == 65001;
 #  else
-inline constexpr bool __use_unicode = true;
+inline constexpr bool __use_unicode_execution_charset = true;
 #  endif
 
 _LIBCPP_HIDE_FROM_ABI inline bool __is_terminal(FILE* __stream) {
@@ -333,7 +333,7 @@ __vprint_unicode([[maybe_unused]] FILE* __stream,
 template <class... _Args>
 _LIBCPP_HIDE_FROM_ABI void print(FILE* __stream, format_string<_Args...> __fmt, _Args&&... __args) {
 #  ifndef _LIBCPP_HAS_NO_UNICODE
-  if constexpr (__print::__use_unicode)
+  if constexpr (__print::__use_unicode_execution_charset)
     __print::__vprint_unicode(__stream, __fmt.get(), std::make_format_args(__args...), false);
   else
     __print::__vprint_nonunicode(__stream, __fmt.get(), std::make_format_args(__args...), false);
@@ -353,7 +353,7 @@ _LIBCPP_HIDE_FROM_ABI void println(FILE* __stream, format_string<_Args...> __fmt
   // Note the wording in the Standard is inefficient. The output of
   // std::format is a std::string which is then copied. This solution
   // just appends a newline at the end of the output.
-  if constexpr (__print::__use_unicode)
+  if constexpr (__print::__use_unicode_execution_charset)
     __print::__vprint_unicode(__stream, __fmt.get(), std::make_format_args(__args...), true);
   else
     __print::__vprint_nonunicode(__stream, __fmt.get(), std::make_format_args(__args...), true);