gh-36814: Fast cardinality method for IntegerVectorsModPermutationGroup
    
# Fast cardinality method for IntegerVectorsModPermutationGroup

This patch fixes #36787 by implementing a `cardinality` method for
`IntegerVectorsModPermutationGroup_with_constraints`.  The method
calculates the cardinality using the the [Polya enumeration
theorem](https://en.wikipedia.org/wiki/P%C3%B3lya_enumeration_theorem)
(also known as the cycle index theorem).

It is faster than the the default implementation, which iterates through
the full set to
find the cardinality.

Incidentally this PR fixes also #36681 so that cardinality and iter no
longer crash in empty-domain situations.

### 📝 Checklist

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### ⌛ Dependencies

- #36873: we can use `is_trivial` from that PR
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URL: #36814
Reported by: Jukka Kohonen
Reviewer(s): Dima Pasechnik, Jukka Kohonen, Martin Rubey, Travis Scrimshaw

Author: Release Manager