Simple way for objective completion to influence the world

[xsebek]

Is your feature request related to a problem? Please describe.

The move tutorial is inefficient because it places many robots that place walls after an objective is met.

^{Each new room is placed after the robot reaches the door.}

Describe the solution you'd like

Add a after: objective ID field to scenario robots and place (and run one tick) them after that objective is met.

This will lower the number of active robots and should scale well with larger scenarios.

Describe alternatives you've considered

• The attribute could cause the waiting robots to wake once that objective is met.

• The objective could directly change the world map, but it seems more complicated.

Additional context

This "objective met event" would dramatically simplify and speed up the move tutorial. See #2064

[byorgey]

An alternative design might be to add a variant of watch/surveil by which a robot can register its desire to be woken upon completion of a specific objective. I am not sure which would be better.