Removes unneeded test dependency on cugraph from pylibcugraph tests

[rlratzel]

closes #2737

• Uses the same util from pylibcugraph.testing instead of cugraph.testing
• Removes a renumbering test that uses cugraph/cudf and instead relies on the test that uses cupy that provides the same coverage

[vyasr]

Thanks for the quick turnaround on this!

[codecov-commenter]

Codecov Report

❗ No coverage uploaded for pull request base (branch-22.10@f0c1e99). Click here to learn what that means.
Patch has no changes to coverable lines.

❗ Current head 694ae06 differs from pull request most recent head 6223994. Consider uploading reports for the commit 6223994 to get more accurate results

Additional details and impacted files

@@               Coverage Diff               @@
##             branch-22.10    #2738   +/-   ##
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  Coverage                ?   59.79%           
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  Files                   ?      111           
  Lines                   ?     6184           
  Branches                ?        0           
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  Hits                    ?     3698           
  Misses                  ?     2486           
  Partials                ?        0           

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[BradReesWork]

@gpucibot merge