Added pylibcugraph utility for setting up return array values

[rlratzel]

Refactored common code that copies device arrays returned by cugraph_* C APIs to cupy arrays into a utility function. This eliminates a significant amount of repeated code, and will be especially helpful as new pylibcugraph APIs are added that copy the existing patterns.

Tested by running existing pylibcugraph unit tests.

[codecov-commenter]

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[betochimas]

I think it's a good idea to expand utils.pyx for future wrappers, so this looks great

[rlratzel]

Tests failed because cudf raised an ImportError due to a missing symbol. Rerunning to get the latest cudf build.

rerun tests

[rlratzel]

@gpucibot merge