fluidAmountRequested

Returns the amount of the given fluid that the machine wants to receive next tick.

If you have a machine that consumes 100 water per second, it should request 100*deltaSeconds of water, and return 0 for every other fluid.

Any implementation of this method must NEVER call the same method for any other connection point, otherwise you risk creating infinite loops.

Called at most once for any given fluid type per tick.