Graph primitives memory scaling improvements for low average vertex degree graphs and many GPUs (Part 1)

[seunghwak]

This PR updates graph primitives to take wrappers for row/column properties. This will enable us to pick either contiguous array or (key, value) pairs inside the wrapper based on the number of GPUs and the average vertex degree (compare V/sqrt(P) & E/P).

[codecov-commenter]

Codecov Report

Merging #1801 (b34ef29) into branch-21.10 (bf64c2c) will increase coverage by 9.17%.
The diff coverage is n/a.

❗ Current head b34ef29 differs from pull request most recent head 8e9f472. Consider uploading reports for the commit 8e9f472 to get more accurate results

@@               Coverage Diff                @@
##           branch-21.10    #1801      +/-   ##
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+ Coverage         59.85%   69.03%   +9.17%     
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  Files                77      139      +62     
  Lines              3547     8425    +4878     
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+ Hits               2123     5816    +3693     
- Misses             1424     2609    +1185     

Impacted Files	Coverage Δ
python/cugraph/cugraph/__init__.py	100.00% <ø> (ø)
python/cugraph/cugraph/_version.py	44.40% <ø> (ø)
python/cugraph/cugraph/centrality/__init__.py	100.00% <ø> (ø)
...graph/cugraph/centrality/betweenness_centrality.py	90.00% <ø> (ø)
python/cugraph/link_prediction/jaccard.py
python/cugraph/traversal/ms_bfs.py
python/cugraph/community/triangle_count.py
python/cugraph/dask/traversal/sssp.py
python/cugraph/layout/force_atlas2.py
python/cugraph/link_prediction/overlap.py
... and 202 more

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[ChuckHastings]

Like the dummy_properties_t change. Definitely makes that easier to understand.

[ChuckHastings]

@gpucibot merge