Allow zero-tick recipes to apply immediately

[kostmo]

Summary

This PR allows a recipe's effects to be applied within the same tick if time: 0 is specified for the recipe.

The previous behavior was that if the time of the recipe was zero, it would nonetheless behave the same as time: 1, and the entity updates would not be applied until the next tick.

This new behavior is useful when "abusing" the drill command to emulate various other games via help from a system robot.

Motivation

For the "Lights Out" game (#1273) I have implemented a system robot that instant-ly toggles the four adjacent lights and the center light when a center light is drill-ed by the player. The light entities are named "off" and "on".

I did some experiments to see if the system robot would react "fast enough" if the player drilled quickly in succession.

Experiments

The 5x5 light grid is initially "off". I moved the player robot to the center of the grid, facing east. From this position, I tried three command sequence variations both before and after this PR. The recipes for toggling lights specify time: 0.

Before this PR

1. Drilling twice in succession

drill down; drill left;

This resulted in an error:

so only the first drill got applied:

This is because I believe the sequence of events was:

Tick / Robot	Action
Tick 1: Player	Execute the first drill command, queue entity modification
Tick 1: System	No changes observed
Tick 2: Player	Entity modification from first drill is applied. Execute second drill command, queue second entity modifications
Tick 2: System	Observe modified entity, toggle the adjacent lights
Tick 3: Player	Try to apply entity modification from second drill command. Throw an error because the system robot has toggled the drill's target entity to on whereas the drill was initially executed when it was still off.

2. Instant for both drills

instant $ (drill down; drill left)

In this case, both of the player's drill commands were executed, but the system robot then failed to doubly-invert one of the cells:

This is due to some kind of race condition in the system robot's logic. However, it is irrelevant because the instant command shall not be available to the player.

3. Instant for first drill only, then second drill

instant (drill down); drill left;

This accomplished what approach number 1 was supposed to; both drill commands were applied and the two overlapping cells got properly inverted:

Explanation: In this case, the entire drilling operation (including applying all effects to entities on the ground) was completed within the player's first tick, so the system robot updated the lights appropriately on its turn. Then, in the next tick the player robot applied another drill command, and again the system robot appropriately did another inversion on the two overlapping middle cells.

After this PR

1. Drilling twice in succession

drill down; drill left;

Now works as expected:

2. and 3.

Behaved identically to before the PR.

[kostmo]

How's it look now?

[byorgey]

Looks good!