Live edits

When the player edits the map, there's an efficient process for applying the edits at the map model and rendering layer. In the middle of a simulation, it's less obvious how to apply all edits. Most of the time currently, edits cause the simulation to reset to midnight. Applying edits to the sim without reset is important for running machine learning experiments and for improving the gameplay experience (by having more immediate feedback about the consequences of a change).

The UI has a dirty_from_edits bit to track when changes have been applied without reset. This lets us tell the player that by the end of the day, any score / results are tentative, because their edits might have a different effect earlier in the day.

What works today

Changes to traffic signals are simple -- incremental_edit_traffic_signal happens at the map layer, and then handle_live_edited_traffic_signals at the sim layer just resets the current stage to 0 if the previous configuration had more stages.

TODO: Recalculating paths

Many of the edits will influence routes. For trips that haven't started yet, as long as pathfinding_upfront is disabled (currently the default), there's nothing to do. For currently active trips, in some cases, rerouting would be ideal but not necessary (like if speed limits changed). In other cases -- like changing access restrictions, modifying lane types, closing intersections -- the route must be recomputed. As a simple first attempt, we could just abort all active trips whose path crosses an edited road or intersection. Later, we can figure out rerouting.

And actually, the only other case to handle is ChangeRouteSchedule, which should just be rescheduling the StartBus commands.

TODO: Parking

What happens if you modify a parking lane while there are cars on it? For now, just delete them. Trips later making use of them will just act as if the car never had room to be spawned at all and be aborted or fallback to walking.

A better resolution would be to relocate them to other parking spots. If the owner is home, it'd be neat to have them walk outside, move the car, and go back in. But this greatly complicates the simulation -- the edited lane is in a transition state for a while, it modifies schedules, the person might not be around, etc.