[refactoring] use new Unity Input System

[route1rodent]

It requires a lot of refactoring and it has some tricky parts that need to be addressed manually (like detecting direction button is being pressed and hold), but it's worth to integrate as it is more future-proof and flexible than traditional input.

Quick Start Guide:
https://github.com/Unity-Technologies/InputSystem/blob/develop/Packages/com.unity.inputsystem/Documentation~/QuickStartGuide.md#getting-input-indirectly-through-an-input-action

Video Tutorial (outdated):
https://www.youtube.com/watch?v=Pzd8NhcRzVo

[route1rodent]

done, also integrated some ideas from @caogtaa like the "input focus/target"
this will help to switch the focus for example to the UI whenever we integrate menus