tree-wide: Sort includes

This was done by running a locally built clang-format with
https://github.com/llvm/llvm-project/pull/137617 and
https://github.com/llvm/llvm-project/pull/137840 applied on all .c
and .h files.

src/tmpfiles/test-offline-passwd.c

@@ -2,10 +2,10 @@
 
 #include <getopt.h>
 
-#include "offline-passwd.h"
-#include "user-util.h"
 #include "format-util.h"
+#include "offline-passwd.h"
 #include "tests.h"
+#include "user-util.h"
 
 static char *arg_root = NULL;