Add `cycles` for `PermGroupElem`

[joschmitt]

A function cycles is requested for PermGroupElem in https://github.com/oscar-system/Oscar.jl/pull/3439#discussion_r1515993975 . Here is an easy implementation of this by calling the AbstractAlgebra function cycledec. I find this a bit weird since the element must know its cycles on the GAP side; after all it prints as a cycle decomposition. I didn't find out how to access this piece of information directly though.

AbstractAlgebra also has a fancy iterator type for the cycles. I don't see a reason for this (other than nicer printing maybe?).