[Game Play] Implement fire rate for stun rocket

[EvoLandEco]

There should also be a cool down time for the stun rocket

[EvoLandEco]

Stun rocket belongs to the projectile class

[EvoLandEco]

Shooting cooldown does not work on stun rocket at the moment.

Similar to #513 #518, we may add tests like this:

#define FIX_ISSUE_517
#ifdef FIX_ISSUE_517
// Player enters cool down status after shooting stun rocket
  {
    game g;
    g.do_action(0, action_type::shoot_stun_rocket);
    g.tick();
    assert(g.get_player(0).is_cooling_down());
    g.do_action(0, action_type::shoot_stun_rocket);
    assert(!g.get_player(0).is_shooting_stun_rocket());
  }

  // Player can shoot stun rocket again after the cool down interval, player cannot shoot stun rocket during the interval
  {
    game g;
    g.do_action(0, action_type::shoot_stun_rocket);
    for (auto i = 0; i < projectile::m_fire_rate - 1; ++i)
      {
        g.tick();
        assert(g.get_player(0).is_cooling_down());
        g.do_action(0, action_type::shoot_stun_rocket);
        assert(!g.get_player(0).is_shooting_stun_rocket());
      }
    g.tick();
    assert(!g.get_player(0).is_cooling_down());
    g.do_action(0, action_type::shoot_stun_rocket);
    assert(g.get_player(0).is_shooting_stun_rocket());
  }

  // Player 0 enters cool down status will not affect other players
  {
    game g;
    g.do_action(0, action_type::shoot_stun_rocket);
    g.tick();
    assert(g.get_player(0).is_cooling_down());
    assert(!g.get_player(1).is_cooling_down());
    assert(!g.get_player(2).is_cooling_down());
  }
  #endif