Boats push creatures in water out of the way

[mlangsdorf]

Summary

SUMMARY: Features "Boats push creatures in water out of the way"

Purpose of change

One of the gating factors for adding Boats to mainline is the issue where boats on deep water will collide with invisible fishes, wrecking the boat's hull.

Change that so the fish get pushed out of the way.

Describe the solution

when a vehicle part collides with a creature while the creature is on a water tile, displace the creature 2 tiles on a 45 degree angle away from the vehicle's direction of movement until the creature is no longer colliding with the vehicle and the creature is not in the same tile as any other creature.

Also, make sure that non-friendly monsters that end up riding in a vehicle can still move around.

Describe alternatives you've considered

It may be necessary to use a variant of get_points() that returns the vehicle's future points, not current points.

Additional context

About to run into a flock of ducks at 20 mph:

Ducks get displaced without damaging the vehicle:

[Night-Pryanik]

While pushing most fish is ok (even the ones like perch weighing 40 kilograms (though I personally think that's a bug that need to be fixed)), jawed terror is a notable example of monster whose weight must be taken into account, I think.

[Zireael07]

How much does the jawed terror weight? An average modern boat is on the order of a ton, if not two.