Kernel: More PID/TID typing

Author: https://github.com/BenWiederhake
Commit: bee08a4b9f
Pull-request: https://github.com/SerenityOS/serenity/pull/3057
Reviewed-by: https://github.com/alimpfard
Reviewed-by: https://github.com/awesomekling
Reviewed-by: https://github.com/bgianfo

Kernel/init.cpp

@@ -336,7 +336,7 @@ void init_stage2()
     tty0->set_graphical(!text_mode);
     Thread* thread = nullptr;
     auto userspace_init = kernel_command_line().lookup("init").value_or("/bin/SystemServer");
-    Process::create_user_process(thread, userspace_init, (uid_t)0, (gid_t)0, (pid_t)0, error, {}, {}, tty0);
+    Process::create_user_process(thread, userspace_init, (uid_t)0, (gid_t)0, ProcessID(0), error, {}, {}, tty0);
     if (error != 0) {
         klog() << "init_stage2: error spawning SystemServer: " << error;
         Processor::halt();