Make firebots spray firefighting foam instead of water

[Berrik]

In my ongoing effort to make the lesser-used robots become useful for people other than those with emags, let's talk about the firebot.

Against anything more than a flaming chemist, spraying water actually makes the fire immeasurably worse, because now the air is full of superheated steam from the water boiling off and the floor is covered with scalding hot liquid after the steam condenses. I think this just got missed when firefighting foam became a thing.

Making it spray foam instead would actually make firebots useful for dealing with giant plasma fires, in the engine or otherwise.