[libc++][NFC] Reorder availability macros in introduction order (#82531)

Reorder the availability macros in __availability to respect the order
in which they were introduced in the dylib. This simple refactor will
greatly simplify an upcoming change I am working on.

Author: ldionne

libcxx/include/__availability

@@ -101,31 +101,38 @@
 #  define _LIBCPP_AVAILABILITY_HAS_BAD_ANY_CAST 1
 #  define _LIBCPP_AVAILABILITY_BAD_ANY_CAST
 
-// These macros controls the availability of __cxa_init_primary_exception
-// in the built library, which std::make_exception_ptr might use
-// (see libcxx/include/__exception/exception_ptr.h).
-#  define _LIBCPP_AVAILABILITY_HAS_INIT_PRIMARY_EXCEPTION 1
-#  define _LIBCPP_AVAILABILITY_INIT_PRIMARY_EXCEPTION
-
 // These macros control the availability of all parts of <filesystem> that
 // depend on something in the dylib.
 #  define _LIBCPP_AVAILABILITY_HAS_FILESYSTEM_LIBRARY 1
 #  define _LIBCPP_AVAILABILITY_FILESYSTEM_LIBRARY
 #  define _LIBCPP_AVAILABILITY_FILESYSTEM_LIBRARY_PUSH
 #  define _LIBCPP_AVAILABILITY_FILESYSTEM_LIBRARY_POP
 
-// This controls the availability of floating-point std::to_chars functions.
-// These overloads were added later than the integer overloads.
-#  define _LIBCPP_AVAILABILITY_HAS_TO_CHARS_FLOATING_POINT 1
-#  define _LIBCPP_AVAILABILITY_TO_CHARS_FLOATING_POINT
-
 // This controls the availability of the C++20 synchronization library,
 // which requires shared library support for various operations
 // (see libcxx/src/atomic.cpp). This includes <barier>, <latch>,
 // <semaphore>, and notification functions on std::atomic.
 #  define _LIBCPP_AVAILABILITY_HAS_SYNC 1
 #  define _LIBCPP_AVAILABILITY_SYNC
 
+// Enable additional explicit instantiations of iostreams components. This
+// reduces the number of weak definitions generated in programs that use
+// iostreams by providing a single strong definition in the shared library.
+//
+// TODO: Enable additional explicit instantiations on GCC once it supports exclude_from_explicit_instantiation,
+//       or once libc++ doesn't use the attribute anymore.
+// TODO: Enable them on Windows once https://llvm.org/PR41018 has been fixed.
+#  if !defined(_LIBCPP_COMPILER_GCC) && !defined(_WIN32)
+#    define _LIBCPP_AVAILABILITY_HAS_ADDITIONAL_IOSTREAM_EXPLICIT_INSTANTIATIONS_1 1
+#  else
+#    define _LIBCPP_AVAILABILITY_HAS_ADDITIONAL_IOSTREAM_EXPLICIT_INSTANTIATIONS_1 0
+#  endif
+
+// This controls the availability of floating-point std::to_chars functions.
+// These overloads were added later than the integer overloads.
+#  define _LIBCPP_AVAILABILITY_HAS_TO_CHARS_FLOATING_POINT 1
+#  define _LIBCPP_AVAILABILITY_TO_CHARS_FLOATING_POINT
+
 // This controls whether the library claims to provide a default verbose
 // termination function, and consequently whether the headers will try
 // to use it when the mechanism isn't overriden at compile-time.
@@ -137,29 +144,22 @@
 #  define _LIBCPP_AVAILABILITY_HAS_PMR 1
 #  define _LIBCPP_AVAILABILITY_PMR
 
-// This controls the availability of the C++20 time zone database.
-// The parser code is built in the library.
-#  define _LIBCPP_AVAILABILITY_HAS_TZDB 1
-#  define _LIBCPP_AVAILABILITY_TZDB
+// These macros controls the availability of __cxa_init_primary_exception
+// in the built library, which std::make_exception_ptr might use
+// (see libcxx/include/__exception/exception_ptr.h).
+#  define _LIBCPP_AVAILABILITY_HAS_INIT_PRIMARY_EXCEPTION 1
+#  define _LIBCPP_AVAILABILITY_INIT_PRIMARY_EXCEPTION
 
 // This controls the availability of C++23 <print>, which
 // has a dependency on the built library (it needs access to
 // the underlying buffer types of std::cout, std::cerr, and std::clog.
 #  define _LIBCPP_AVAILABILITY_HAS_PRINT 1
 #  define _LIBCPP_AVAILABILITY_PRINT
 
-// Enable additional explicit instantiations of iostreams components. This
-// reduces the number of weak definitions generated in programs that use
-// iostreams by providing a single strong definition in the shared library.
-//
-// TODO: Enable additional explicit instantiations on GCC once it supports exclude_from_explicit_instantiation,
-//       or once libc++ doesn't use the attribute anymore.
-// TODO: Enable them on Windows once https://llvm.org/PR41018 has been fixed.
-#  if !defined(_LIBCPP_COMPILER_GCC) && !defined(_WIN32)
-#    define _LIBCPP_AVAILABILITY_HAS_ADDITIONAL_IOSTREAM_EXPLICIT_INSTANTIATIONS_1 1
-#  else
-#    define _LIBCPP_AVAILABILITY_HAS_ADDITIONAL_IOSTREAM_EXPLICIT_INSTANTIATIONS_1 0
-#  endif
+// This controls the availability of the C++20 time zone database.
+// The parser code is built in the library.
+#  define _LIBCPP_AVAILABILITY_HAS_TZDB 1
+#  define _LIBCPP_AVAILABILITY_TZDB
 
 #elif defined(__APPLE__)