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/dbus-execute.c

@@ -2,6 +2,7 @@
 
 #include <sys/mount.h>
 #include <sys/prctl.h>
+
 #include "af-list.h"
 #include "alloc-util.h"
 #include "bus-get-properties.h"