Implement use of the new InputSystem in Unity

[bruskajp]

I'm not sure exactly how this should be done.

Here are the methods I've thought of

1. Remove all instances of Input and replace with InputManager and then switch the InputManager over to use InputSystem
2. Remove InputManager, remove all instances of Input and replace with InputSystem, then
   1. Implement a new pause system that uses onEvent so it doesn't have to use an action map (and can never be ignored)
   2. Implement a new pause system that uses a pauseMenu action map and turns off all other action maps
      (https://www.youtube.com/watch?v=UGh4exLCFRg)
      • This may require a PauseScreen class