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/shared/exec-util.c

@@ -2,10 +2,10 @@
 
 #include <dirent.h>
 #include <errno.h>
+#include <stdio.h>
 #include <sys/prctl.h>
 #include <sys/types.h>
 #include <unistd.h>
-#include <stdio.h>
 
 #include "alloc-util.h"
 #include "bitfield.h"