Add package to the list of dependencies

[jnke2016]

A breaking pytest change removed the py package from its list of dependencies causing the SG/MG tests to fail.
This PR adds the package to our list of dependencies.
In addition to the above, this PR also:

1. Reduces the value of the fanout_vals when testing uniform_neighbor_sampling
2. Updates the ownership transfer of device_buffer_unique_ptr to cuDF buffer through the call as_buffer()

closes #2857
closes #2881

[jnke2016]

rerun tests

[msadang]

rerun tests

[ChuckHastings]

rerun tests

[msadang]

py and range changes look good.

[BradReesWork]

@gpucibot merge

[codecov-commenter]

Codecov Report

❗ No coverage uploaded for pull request base (branch-22.12@1a1d52f). Click here to learn what that means.
Patch has no changes to coverable lines.

❗ Current head e93f5ba differs from pull request most recent head 1057666. Consider uploading reports for the commit 1057666 to get more accurate results

Additional details and impacted files

@@               Coverage Diff               @@
##             branch-22.12    #2858   +/-   ##
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  Coverage                ?   46.64%           
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  Files                   ?      114           
  Lines                   ?     6395           
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  Hits                    ?     2983           
  Misses                  ?     3412           
  Partials                ?        0           

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[BradReesWork]

@gpucibot merge