libstdc++: Optimize std::is_bounded_array compilation performance

This patch optimizes the compilation performance of std::is_bounded_array
by dispatching to the new __is_bounded_array built-in trait.

libstdc++-v3/ChangeLog:

	* include/std/type_traits (is_bounded_array_v): Use
	__is_bounded_array built-in trait.

Signed-off-by: Ken Matsui <kmatsui@gcc.gnu.org>

libstdc++-v3/include/std/type_traits

@@ -3498,11 +3498,16 @@ template<typename _Ret, typename _Fn, typename... _Args>
   /// True for a type that is an array of known bound.
   /// @ingroup variable_templates
   /// @since C++20
+# if _GLIBCXX_USE_BUILTIN_TRAIT(__is_bounded_array)
+  template<typename _Tp>
+    inline constexpr bool is_bounded_array_v = __is_bounded_array(_Tp);
+# else
   template<typename _Tp>
     inline constexpr bool is_bounded_array_v = false;
 
   template<typename _Tp, size_t _Size>
     inline constexpr bool is_bounded_array_v<_Tp[_Size]> = true;
+# endif
 
   /// True for a type that is an array of unknown bound.
   /// @ingroup variable_templates