[libc++] Split the various iterator types out of <iterator>

Differential Revision: https://reviews.llvm.org/D104669

NOKEYCHECK=True
GitOrigin-RevId: f32f3db9fcbf43b1a603c5da882557ebed62f1c5
diff --git a/include/string b/include/string
index 9b76be3..c5e0745 100644
--- a/include/string
+++ b/include/string
@@ -516,6 +516,7 @@
 #include <__config>
 #include <__debug>
 #include <__functional_base>
+#include <__iterator/wrap_iter.h>
 #include <algorithm>
 #include <compare>
 #include <cstdio>  // EOF