Code cleanup

[seunghwak]

As a pre-requisite to address #2600

• add utility functions to compute local degrees (for the entire set of majors & a subset of the majors) and the sum of local degrees (for a subset of the majors) to edge_partition_device_view_t
• Replace raw pointers with raft::device_span in multiple places of graph_view_t, edge_partition_view_t, and edge_partition_device_view_t
• cugraph::test::to_host was previously defined, but used only in a subset of C++ tests, update to_host to take both raft::device_span and rmm::device_uvector as input arguments and use this (instead of update_host) in most of the C++ tests (except for some legacy sampling tests).

Breaking as some functions in graph_view_t, edge_partition_view_t and edge_partition_device_view_t are updated to return raft::device_span instead of a raw pointer (these functions are used only internally AFAIK, but still a breaking change in the public API).

[codecov-commenter]

Codecov Report

❗ No coverage uploaded for pull request base (branch-22.10@1f83c6b). Click here to learn what that means.
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❗ Current head 301f75a differs from pull request most recent head 06f0115. Consider uploading reports for the commit 06f0115 to get more accurate results

Additional details and impacted files

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  Hits                    ?     3697           
  Misses                  ?     2457           
  Partials                ?        0           

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[ChuckHastings]

rerun tests

[naimnv]

Thanks Seunghwa for pointing me to major changes.

[ChuckHastings]

@gpucibot merge