Put ZZ in InfiniteEnumeratedSets.
Merge branch 'develop' into t/16239/public/categories/fix_ZZ-16239
16239: Fix Parent._list_from_iterator_cached instead of implementing a new ZZ.list

For consistency with EnumeratedSets category, and as a preliminary
toward just using it, Parent._list_from_iterator_cached now:

- raises a NotImplementedError rather than a value error for an
  infinite parent
- Uses the category Sets().Infinite() instead of the method
  `is_finite` (which might be costly, not implemented, ...) to decide
  whether the parent is infinite or not

With this, it's not necessary anymore to implement ZZ.list.
Fixed all broken doctests.
16239: final proofreading with Travis looking over my shoulder
Merge branch 'public/categories/fix_ZZ-16239' of trac.sagemath.org:sage into public/categories/fix_ZZ-16239
Reverted change for check for infinite enumerated sets.
Ellipsize the source line number in warnings
Check doctest output for source line numbers
16239: added comment for the current workaround in Parent._list_from_iterator_cached
Merge #16622

Conflicts:
	src/sage/combinat/designs/incidence_structures.py
Trac #16626: ellipsis for doctest line numbers

Warnings (including deprecations) should be of the form
{{{
   sage: raise_warning()
   doctest:...: Warning: this is a warning
}}}
Note the ellipsis. Putting the actual source line number in there is not
cool.

URL: http://trac.sagemath.org/16626
Reported by: vbraun
Ticket author(s): Volker Braun
Reviewer(s): Martin Albrecht, Dima Pasechnik
Trac #16239: ZZ in the wrong category

{{{
sage: ZZ.categories()
[Category of euclidean domains,
 Category of principal ideal domains,
 Category of unique factorization domains,
 Category of gcd domains,
 Category of integral domains,
 Category of domains,
 Category of commutative rings,
 Category of rings,
 Category of rngs,
 Category of semirings,
 Category of monoids,
 Category of semigroups,
 Category of magmas,
 Category of commutative additive groups,
 Category of commutative additive monoids,
 Category of commutative additive semigroups,
 Category of additive magmas,
 Category of sets,
 Category of sets with partial maps,
 Category of objects]
}}}
Notice that it is not an infinite enumerated set.

URL: http://trac.sagemath.org/16239
Reported by: tscrim
Ticket author(s): Travis Scrimshaw
Reviewer(s): Nicolas M. Thiéry