[libc++] Alphabetize and include-what-you-use. NFCI.

Differential Revision: https://reviews.llvm.org/D102781

NOKEYCHECK=True
GitOrigin-RevId: bfbd73f87d7b2c1140b43192cea6b7fbbfc35cd0
diff --git a/include/bit b/include/bit
index 7708106..c64e45c 100644
--- a/include/bit
+++ b/include/bit
@@ -55,7 +55,7 @@
 */
 
 #include <__config>
-#include <__bits>
+#include <__bits> // __libcpp_clz
 #include <__debug>
 #include <limits>
 #include <type_traits>