Call the generator helper method directly instead of calling`PyIter_Next` when calling a native generator from a native function.This way we can avoid raising StopIteration when the generator isexhausted. The approach is similar to what I used to speed up callsusing await in#19398. Refer to that PR for a more detailed explanation.This helps mostly when a generator produces a small number of values,which is quite common.This PR improves the performance of this microbenchmark, which is aclose to the ideal use case, by about 2.6x (now 5.7x faster thaninterpreted):```from typing import Iteratordef foo(x: int) -> Iterator[int]:    for a in range(x):        yield adef bench(n: int) -> None:    for i in range(n):        for a in foo(1):            passfrom time import timebench(1000 * 1000)t0 = time()bench(50 * 1000 * 1000)print(time() - t0)```

This is another problem caused by#19398 and a missing part of#20254 cc@JukkaL@hauntsaninja there is a small chance this may be related to theproblems with black.

This is another problem caused bypython#19398 and a missing part ofpython#20254 cc@JukkaL@hauntsaninja there is a small chance this may be related to theproblems with black.