`drop` methods don't pass value to Iterator while dropping

[avandolder]

i'm a bit confused why this needs a lastValue instead of calling with the parameter absent. why would the next method need to have arguments.length be 0 for the dropped cases, but 1 for the kept ones?

(in other words, why aren't they all passing undefined to IteratorStep?)

Originally posted by @ljharb in #112

The current behaviour of the drop methods is observably different for dropped calls to IteratorStep/Next and non-dropped ones. It seems desirable to unify them; either pass through lastValue to the iterator on all steps, even the dropped ones, or don't pass it at all.

[devsnek]

it was done that way on purpose (drop and then it behaves like map v => v), but I wouldn't be opposed to not passing it at all.

[bakkot]

As of #194 none of the helpers ever pass an argument to .next.