feat(corelib): Iterator::product

[MagisterDaIlis]

will rebase on Iterator::sum once merged

[reviewable-StarkWare]

This change is 

[orizi]

Reviewed 5 of 5 files at r1, all commit messages.
Reviewable status: complete! all files reviewed, all discussions resolved (waiting on @MagisterDaIlis)

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a discussion (no related file):
@gilbens-starkware for 2nd eye.

[gilbens-starkware]

Reviewed 5 of 5 files at r1, all commit messages.
Reviewable status: complete! all files reviewed, all discussions resolved (waiting on @MagisterDaIlis)

[gilbens-starkware]

Reviewable status: all files reviewed, 1 unresolved discussion (waiting on @MagisterDaIlis)

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corelib/src/test/iter_test.cairo line 78 at r1 (raw file):

    assert_eq!((0_usize..=0).into_iter().product(), 1);
    assert_eq!((0_usize..=1).into_iter().product(), 1);
    assert_eq!((0_usize..=5).into_iter().product(), 120);

Suggestion:

    assert_eq!((1_usize..=0).into_iter().product(), 1);
    assert_eq!((1_usize..=1).into_iter().product(), 1);
    assert_eq!((1_usize..=5).into_iter().product(), 120);

[MagisterDaIlis]

Reviewable status: 2 of 5 files reviewed, 1 unresolved discussion (waiting on @gilbens-starkware and @orizi)

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corelib/src/test/iter_test.cairo line 78 at r1 (raw file):

    assert_eq!((0_usize..=0).into_iter().product(), 1);
    assert_eq!((0_usize..=1).into_iter().product(), 1);
    assert_eq!((0_usize..=5).into_iter().product(), 120);

Done.

[gilbens-starkware]

Reviewed 3 of 3 files at r2, all commit messages.
Reviewable status: complete! all files reviewed, all discussions resolved (waiting on @MagisterDaIlis)