feat: add `cross_join`

[iajoiner]

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Rationale for this change

Now let's add the simplest form of join without adding its proof yet, that is, the cross join. Cross joins are not that common but they are easier to implement than inner joins since they don't require sorting or matching.

What changes are included in this PR?

• add cross_join

  Yes.

[github-actions[bot]]

:tada: This PR is included in version 0.50.1 :tada:

The release is available on GitHub release

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