[libc++] Alphabetize header inclusions and include-what-you-use <__debug>. NFCI.

NOKEYCHECK=True
GitOrigin-RevId: 06b40e80aefc9a7ccf2efbf7717037bd103a779c
diff --git a/include/fstream b/include/fstream
index 5006923..dd1aa72 100644
--- a/include/fstream
+++ b/include/fstream
@@ -181,11 +181,12 @@
 
 #include <__config>
 #include <__availability>
-#include <ostream>
-#include <istream>
+#include <__debug>
 #include <__locale>
 #include <cstdio>
 #include <cstdlib>
+#include <istream>
+#include <ostream>
 
 #if !defined(_LIBCPP_HAS_NO_FILESYSTEM_LIBRARY)
 #   include <filesystem>