Decoupling UI event handler and game simulation

[TristanCacqueray]

Is your feature request related to a problem? Please describe.
When the game is running slow, as with the game of life scenario, the UI is not responsive.

Describe the solution you'd like
The game simulation, e.g. the robot ticks, should happen in a dedicated thread, outside of the brick event handler.
However this is presently not possible because of the tight coupling between UI and Game state.
In order to achieve this feature, it seems like we need to:

• Changes handleEvent :: BrickEvent Name AppEvent -> EventM Name AppState () to handleEvent :: GameState -> BrickEvent Name AppEvent -> EventM Name UIState ().
• Use some sort of a signal callback so that the UI can change the GameState, e.g. signal Pause.
• Handle the game simulation in place of using the Frame bchan forever loop, and interpret the signal event asynchronously.

[xsebek]

This would be very useful in scenarios with many robots, like the move tutorial. #2064

The FPS/TPS widget would probably also work better when separated. #2061

Eventually, something tells me players might be tempted to create whole swarms of robots and run into freezing UI. I am going to raise the severity.

[TristanCacqueray]

Please note that I wrote this issue after the first swarm swarm, and that the description is not really thought-out. Perhaps this could also supports a future GUI, like a OpenGL render would be pretty neat :-)

Keep up the good work!