Allow player to continue playing after the end of a turn. (#3526)

This PR:

Keeps track of time spent in mission 

Introduces a new "turnless mode" setting, which activates the following:
- At the end of a mission, fast forwards through the time spent in the
mission, skipping any combat (which has already been tracked through
state.json)
- Removes killed flights from the ATO
- Does not start a new turn, instead allows the player to continue the
current turn.

game/sim/gameloop.py

@@ -100,7 +100,11 @@ class GameLoop:
         if not self.started:
             raise RuntimeError("Attempted to tick game loop before initialization")
         try:
-            self.sim.tick(self.events)
+            self.sim.tick(
+                self.events,
+                self.game.settings.combat_resolution_method,
+                force_continue=False,
+            )
             self.completed = self.events.simulation_complete
             if not suppress_events:
                 self.send_update(rate_limit=True)