Overwatch 2 doesn't like the win32u `-syscall` conversion that happened a while back, because it hooks KiUserCallbackDispatcher. This MR fixes it up to match what Overwatch 2 expects.
-- v3: ntdll: Pass KiUserCallbackDispatcher parameters on stack. ntdll: Add 5-byte nop to start of KiUserCallbackDispatcher. ntdll: Align stack pointer when calling KiUserCallbackDispatcher.