fix(corelib): Take::nth(usize::MAX) returns None instead of overflowing - #10022

Summary

Fixes an integer overflow in Take::nth() when called with n = usize::MAX. Previously, the implementation computed n + 1 directly before calling checked_sub, which would overflow when n is usize::MAX. The fix splits the operation into two checked steps: first using checked_add(1) on n, then passing the result to checked_sub, so that overflow is handled safely and None is returned instead of panicking or producing incorrect results.

Type of change

Please check one:

• Bug fix (fixes incorrect behavior)
• New feature
• Performance improvement
• Documentation change with concrete technical impact
• Style, wording, formatting, or typo-only change

Why is this change needed?

Calling iter.take(n).nth(usize::MAX) would overflow when computing n + 1 before the checked subtraction, causing incorrect behavior instead of safely returning None.

What was the behavior or documentation before?

Take::nth(usize::MAX) would overflow on the n + 1 arithmetic, since the addition was performed before any overflow check.

What is the behavior or documentation after?

Take::nth(usize::MAX) now correctly returns None without overflowing, because n.checked_add(1) is evaluated first and short-circuits the rest of the expression on overflow.

Related issue or discussion (if any)

None.

Additional context

A regression test was added to iter_test.cairo to assert that nth(usize::MAX) returns None on a Take iterator, preventing this overflow from being reintroduced.