Add CPO test

Author: H-G-Hristov

libcxx/test/std/library/description/conventions/customization.point.object/cpo.compile.pass.cpp

@@ -81,6 +81,9 @@ static_assert(test(std::ranges::ssize, a));
 // views::empty<T> is not a CPO
 static_assert(test(std::views::iota, 1));
 static_assert(test(std::views::iota, 1, 10));
+#if TEST_STD_VER >= 26
+static_assert(test(std::views::indices, 10));
+#endif
 //static_assert(test(std::views::istream<int>, 1);
 static_assert(test(std::views::single, 4));