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/executor.c

@@ -12,11 +12,11 @@
 #include "cgroup.h"
 #include "dynamic-user.h"
 #include "exec-invoke.h"
-#include "execute-serialize.h"
 #include "execute.h"
+#include "execute-serialize.h"
 #include "exit-status.h"
-#include "fdset.h"
 #include "fd-util.h"
+#include "fdset.h"
 #include "fileio.h"
 #include "getopt-defs.h"
 #include "label-util.h"