Message 339617 - Python tracker

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Content 
This patch makes it slow for small iterators:

Perf program:

import perf

runner = perf.Runner()
runner.timeit("list_comp",
               stmt="[x for x in range(10)]",
               setup="")


Current master:
❯ ./python.exe ../check.py
.....................
list_comp: Mean +- std dev: 3.97 us +- 0.15 us

PR 12718:
❯ ./python.exe ../check.py
.....................
list_comp: Mean +- std dev: 4.57 us +- 0.17 us

The overhead is very likely due to calling __length_hint__