feat(corelib): add iterator traits to prelude

[cairolover]

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[orizi]

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

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corelib/src/lib.cairo line 392 at r1 (raw file):

pub mod iter;
#[allow(unused_imports)]
use iter::{IntoIterator, Iterator};

[orizi]

Reviewed 4 of 6 files at r1, 1 of 1 files at r2, all commit messages.
Reviewable status: all files reviewed, 1 unresolved discussion (waiting on @cairolover)

[gilbens-starkware]

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