The results screen knows who wins

[TheoPannetier]

Depends

• [ ] #718
• [x] #721

Context

The results screen should know who wins the game and display it, so it should be able to fetch this info from the game.

Test

Below is a proposed test, feel free to adapt as necessary.

// (720) The results screen knows who is winning
{
  game_view gv;
  player &player_two = gv.get_game().get_player(1);
  player_two.grow();
  const int winner = gv.get_results_screen().get_winner();
  assert(winner == 1);
}