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/systemctl/systemctl-start-unit.c

@@ -12,9 +12,9 @@
 #include "macro.h"
 #include "special.h"
 #include "string-util.h"
+#include "systemctl.h"
 #include "systemctl-start-unit.h"
 #include "systemctl-util.h"
-#include "systemctl.h"
 #include "terminal-util.h"
 
 static const struct {