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/core/execute-serialize.c

@@ -8,9 +8,9 @@
 #include "escape.h"
 #include "exec-credential.h"
 #include "execute-serialize.h"
-#include "hexdecoct.h"
 #include "fd-util.h"
 #include "fileio.h"
+#include "hexdecoct.h"
 #include "in-addr-prefix-util.h"
 #include "parse-helpers.h"
 #include "parse-util.h"