Update primitives to support DCSR (DCSC) segments (Part 2/2)

[seunghwak]

• Update key-based primitives (used by Louvain) to reduce thread-divergence
• Update key-based primitives (used by Louvain) to support DCSR (DCSC) segments

[codecov-commenter]

Codecov Report

Merging #1703 (a88372d) into branch-21.08 (9bcfa14) will increase coverage by 0.02%.
The diff coverage is n/a.

❗ Current head a88372d differs from pull request most recent head 0828ee9. Consider uploading reports for the commit 0828ee9 to get more accurate results

@@               Coverage Diff                @@
##           branch-21.08    #1703      +/-   ##
================================================
+ Coverage         59.82%   59.85%   +0.02%     
================================================
  Files                77       77              
  Lines              3515     3517       +2     
================================================
+ Hits               2103     2105       +2     
  Misses             1412     1412              

Impacted Files	Coverage Δ
python/cugraph/_version.py	44.80% <0.00%> (+0.39%)	⬆️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 9bcfa14...0828ee9. Read the comment docs.

[BradReesWork]

@gpucibot merge