This is a preparation for better handling of message packing between win32u and user32. It also removes some hacks that were needed before syscall separation completion.
-- v2: win32u: Pass module name before packed lparam in win_hook_params. user32: Always use NtCallbackReturn to pass result from User32CallWindowsHook. wow64win: Convert parameters in place in wow64_NtUserCallWindowsHook. wow64win: Conver parameters in place in wow64_NtUserCallWinProc.