Everywhere: Fix order of includes and #pragma once

Author: https://github.com/BenWiederhake
Commit: c214d31c5e
Pull-request: https://github.com/SerenityOS/serenity/pull/15277

Kernel/Arch/SafeMem.h

@@ -4,12 +4,12 @@
  * SPDX-License-Identifier: BSD-2-Clause
  */
 
+#pragma once
+
 #include <AK/Atomic.h>
 #include <AK/Optional.h>
 #include <AK/Types.h>
 
-#pragma once
-
 namespace Kernel {
 
 struct RegisterState;