Python code cleanup across docs, wrappers, testing

[betochimas]

This PR incorporates suggested changes from issue #2037, opened back in 22.02, as well as cleaning up documentation and testing code from 22.04 work.

Specifically, this PR does the following:

• Removes worker helpers from MNMG algos in the online documentation (e.g. call_katz_centrality, call_louvain, call_wcc)
• Adds helpers from comms such as get_comms, get_session_id, get_2D_partition, is_initialized that were previously missing
• Adds helpers from NumberMap such as from_internal_vertex_id, to_internal_vertex_id, renumber, set_renumbered_col_names
• Add MNMG Hits and Node2vec to docs
• Added docstring descriptions and examples to methods that were missing them
• Fixed docstring examples in egonet.py, node2vec.py
• Adds pylibcugraph docstring examples to the list of examples tested in cugraph/tests/test_doctests.py
• Adds support for MG Dask docstring example testing, tested in newly created cugraph/tests/dask/test_mg_doctests.py

This PR addresses the items from and closes #2227.
This PR also closes #2193.

[codecov-commenter]

Codecov Report

Merging #2194 (220eaf5) into branch-22.06 (728950e) will decrease coverage by 0.10%.
The diff coverage is 21.59%.

❗ Current head 220eaf5 differs from pull request most recent head 9eba1c0. Consider uploading reports for the commit 9eba1c0 to get more accurate results

@@               Coverage Diff                @@
##           branch-22.06    #2194      +/-   ##
================================================
- Coverage         71.33%   71.22%   -0.11%     
================================================
  Files               171      172       +1     
  Lines             11207    11277      +70     
================================================
+ Hits               7994     8032      +38     
- Misses             3213     3245      +32     

Impacted Files	Coverage Δ
...graph/cugraph/centrality/betweenness_centrality.py	89.65% <ø> (ø)
python/cugraph/cugraph/comms/comms.py	70.23% <ø> (+35.71%)	⬆️
python/cugraph/cugraph/community/egonet.py	97.36% <ø> (ø)
...ython/cugraph/cugraph/community/ktruss_subgraph.py	85.29% <ø> (ø)
...cugraph/cugraph/dask/centrality/katz_centrality.py	25.00% <ø> (ø)
python/cugraph/cugraph/dask/common/read_utils.py	86.66% <ø> (ø)
python/cugraph/cugraph/dask/community/louvain.py	25.80% <ø> (-0.67%)	⬇️
...on/cugraph/cugraph/dask/components/connectivity.py	25.92% <ø> (ø)
python/cugraph/cugraph/dask/link_analysis/hits.py	18.36% <ø> (ø)
...hon/cugraph/cugraph/dask/link_analysis/pagerank.py	17.77% <ø> (ø)
... and 12 more

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[betochimas]

rerun tests

[betochimas]

rerun tests

[betochimas]

rerun tests

[rlratzel]

@gpucibot merge