[experiment] Improve loop algorithms crosschecking

The current technique use had a flaw. With algorithm containing
a different number of groups, it would truncate the to the shortest
as explained in the zip function documentation.

Now itertools.zip_longest is used to ensure that the iteration is
done on the longest input.
10 jobs for improve_loop_algorithm_crosscheck in 73 minutes and 51 seconds (queued for 1 second)
Status Job ID Name Coverage
  Build
passed #173139
docker-build
build_linux_36

00:26:32

64.0%
passed #173140
docker-build
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00:26:31

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macosx
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00:18:57

64.0%
canceled #173665
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00:47:19

canceled #173290
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00:27:17

canceled #173160
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build_macosx_37

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failed #173616
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build_macosx_37

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failed #173259
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failed #173138
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build_macosx_37

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