gh-37028: add method to compute the longest (induced) cycle in a (di)graph
This PR adds a method to compute the longest (induced) cycle in a
(di)graph. The method can also consider weighted cases.
This answers a request from https://ask.sagemath.org/question/75124/how-
to-find-a-longest-cycle-and-a-longest-induced-cycle-in-a-graph/
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URL: https://github.com/sagemath/sage/pull/37028
Reported by: David Coudert
Reviewer(s): David Coudert, Travis Scrimshaw
