Move cycle_graph generator to rustworkx-core

[mtreinish]

This commit migrates the cycle-graph generator to rustworkx-core. It makes the function generic so that it can be used with any petgraph graph that's buildable and node indexable. This is primarily to serve as a pattern for migrating all the generator functions we currently have to rustworkx-core. This pattern should be usable for any generator function we have.

Part of #751

TODO:

• Preserve IndexError for python wrapper function
• Add release note about new rustworkx-core module and function
• Tests for rustworkx-core function
• Docs for rustworkx-core function

[coveralls]

Pull Request Test Coverage Report for Build 3850211525

• 71 of 75 (94.67%) changed or added relevant lines in 4 files are covered.
• 1 unchanged line in 1 file lost coverage.
• Overall coverage increased (+0.03%) to 96.955%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
rustworkx-core/src/generators/mod.rs	0	4	0.0%

Files with Coverage Reduction	New Missed Lines	%
src/shortest_path/all_pairs_bellman_ford.rs	1	98.88%

Totals
Change from base Build 3788047570:	0.03%
Covered Lines:	13658
Relevant Lines:	14087

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💛 - Coveralls

[IvanIsCoding]

Overall looks good to me, it is a good framework to migrate the generators. I just made a minor suggestion on imports to avoid having to import every generator by hand given we will have a large amount.