Update Graph to store a Pylibcugraph Graph (SG/MG Graph)

[alexbarghi-nv]

Closes #2373

[alexbarghi-nv]

rerun tests

[codecov-commenter]

Codecov Report

Merging #2394 (50209c8) into branch-22.08 (5dd0267) will increase coverage by 0.50%.
The diff coverage is 66.66%.

❗ Current head 50209c8 differs from pull request most recent head fd3b844. Consider uploading reports for the commit fd3b844 to get more accurate results

@@               Coverage Diff                @@
##           branch-22.08    #2394      +/-   ##
================================================
+ Coverage         60.11%   60.62%   +0.50%     
================================================
  Files               102      102              
  Lines              5155     5234      +79     
================================================
+ Hits               3099     3173      +74     
- Misses             2056     2061       +5     

Impacted Files	Coverage Δ
python/cugraph/cugraph/__init__.py	100.00% <ø> (ø)
python/cugraph/cugraph/dask/common/input_utils.py	22.13% <0.00%> (ø)
python/cugraph/cugraph/dask/common/mg_utils.py	30.43% <0.00%> (ø)
python/cugraph/cugraph/dask/comms/comms.py	34.06% <0.00%> (ø)
...ugraph/cugraph/dask/structure/mg_property_graph.py	18.56% <0.00%> (+0.07%)	⬆️
python/cugraph/cugraph/sampling/node2vec.py	81.81% <ø> (ø)
...ure/graph_implementation/simpleDistributedGraph.py	16.47% <28.57%> (+1.45%)	⬆️
...h/cugraph/dask/sampling/uniform_neighbor_sample.py	23.25% <30.00%> (+6.58%)	⬆️
python/cugraph/cugraph/dask/traversal/bfs.py	33.33% <42.85%> (+18.33%)	⬆️
python/cugraph/cugraph/structure/graph_classes.py	79.48% <50.00%> (ø)
... and 11 more

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[rlratzel]

Looks good, I just had some minor comments and questions.

[rlratzel]

@gpucibot merge