Fix lazy_list.pyx doctests to use picklable iterators

Instead of using try-except to catch unpicklable iterators like
itertools.count (which can't be pickled in Python 3.14), changed
the doctests to use list iterators which ARE picklable.

This properly tests that the __reduce__ method works correctly
while being compatible with Python 3.14's removal of pickle
support for itertools objects.

Author: cxzhong

src/sage/misc/lazy_list.pyx

@@ -534,16 +534,15 @@ cdef class lazy_list_generic():
 
         EXAMPLES::
 
-            sage: from itertools import count
             sage: from sage.misc.lazy_list import lazy_list
-            sage: m = lazy_list(count())
+            sage: m = lazy_list(iter([0, 1, 4, 9, 16, 25, 36, 49, 64, 81]))
             sage: x = loads(dumps(m))
             sage: y = iter(x)
             sage: print("{} {} {}".format(next(y), next(y), next(y)))
-            0 1 2
+            0 1 4
             sage: m2 = m[3::2]
             sage: loads(dumps(m2))
-            lazy list [3, 5, 7, ...]
+            lazy list [9, 25, 49, ...]
         """
         if self.master is None:
             raise NotImplementedError
@@ -916,8 +915,9 @@ cdef class lazy_list_from_iterator(lazy_list_generic):
         [0, 1, 2]
         sage: [next(x), next(y)]
         [3, 3]
-        sage: loads(dumps(m))
-        lazy list [0, 1, 2, ...]
+        sage: m2 = lazy_list(iter([0, 1, 4, 9, 16]))
+        sage: loads(dumps(m2))
+        lazy list [0, 1, 4, ...]
     """
 
     def __init__(self, iterator, cache=None, stop=None):
@@ -986,10 +986,9 @@ cdef class lazy_list_from_iterator(lazy_list_generic):
         TESTS::
 
             sage: from sage.misc.lazy_list import lazy_list_from_iterator
-            sage: from itertools import count
-            sage: loads(dumps(lazy_list_from_iterator(count())))
-            lazy list [0, 1, 2, ...]
-            sage: loads(dumps(lazy_list_from_iterator(count(), ['a'])))
+            sage: loads(dumps(lazy_list_from_iterator(iter([0, 1, 4, 9, 16]))))
+            lazy list [0, 1, 4, ...]
+            sage: loads(dumps(lazy_list_from_iterator(iter([0, 1, 4, 9, 16]), ['a'])))
             lazy list ['a', 0, 1, ...]
         """
         return lazy_list_from_iterator, (self.iterator, self.cache, self.stop)