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/test/test-exec-util.c

@@ -6,8 +6,8 @@
 #include <unistd.h>
 
 #include "alloc-util.h"
-#include "copy.h"
 #include "constants.h"
+#include "copy.h"
 #include "env-util.h"
 #include "exec-util.h"
 #include "fd-util.h"