[libc++] Split up __memory/base.h into meaningful headers

GitOrigin-RevId: f992cfba7173ab55d9795f71156ffde0b5eece0a
diff --git a/include/iterator b/include/iterator
index cddeb9a..4e1077f 100644
--- a/include/iterator
+++ b/include/iterator
@@ -425,7 +425,7 @@
 #include <concepts>
 #include <cstddef>
 #include <initializer_list>
-#include <__memory/base.h>
+#include <__memory/addressof.h>
 #include <__memory/pointer_traits.h>
 #include <version>
 #include <concepts>