feat(utils): add contains function for span

[noa-starkware]

Note

Adds a new span module with a generic contains function to check membership in a Span<T>.

• Utilities:
  • New span module:
    • Add contains<T>(span: Span<T>, value: T) -> bool to check if a Span<T> contains a value.
  • Export span in packages/utils/src/lib.cairo.

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[remollemo]

Reviewable status: 0 of 2 files reviewed, all discussions resolved (waiting on @noa-starkware)