sagemathgh-36814: Fast cardinality method for IntegerVectorsModPermut…

…ationGroup

    
# Fast cardinality method for IntegerVectorsModPermutationGroup

This patch fixes sagemath#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 sagemath#36681 so that cardinality and iter no
longer crash in empty-domain situations.

### 📝 Checklist

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### ⌛ Dependencies

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